1 Form Proposal - Invoice 1.5 crack serial keygen

1 Form Proposal - Invoice 1.5 crack serial keygen

Public Key Cryptography (PKC): Uses one key for encryption and another for decryption; also called asymmetric encryption. Primarily used for authentication, non. Section 1 includes specifications related to the interpretation of the contract. 3.3.1. Detailed descriptions, including make, model, and serial number. 1.5.1. Hold Point - Before the work commences provide Specialist sub-contractor invoices Patch and repair all surfaces. 1 Form Proposal - Invoice 1.5 crack serial keygen

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5.4. DES, Breaking DES, and DES Variants

The Data Encryption Standard (DES) started life in the mid-1970s, adopted by the National Bureau of Standards (NBS) [now the National Institute of Standards and Technology (NIST)] as Federal Information Processing Standard 46 (FIPS PUB 46-3) and by the American National EFT Dongle 2.7 crack latest Archives Institute (ANSI) as X3.92.

As mentioned earlier, DES uses the Data Encryption Algorithm (DEA), a secret key block-cipher employing a 56-bit key operating on 64-bit blocks. FIPS PUB 81 describes four modes of DES operation: Electronic Codebook (ECB), Cipher Block Chaining (CBC), Cipher Feedback (CFB), and Output Feedback (OFB). Despite all of these options, ECB is the most commonly deployed mode of operation.

NIST finally declared DES obsolete in 2004, and withdrew FIPS PUB 46-3, 74, and 81 (Federal Register, July 26, 2004, 69(142), 44509-44510). Although other block ciphers have replaced DES, it is still interesting to see how DES encryption is performed; not only is it sort of neat, but DES was the first crypto scheme commonly seen in non-governmental applications and was the catalyst for modern "public" cryptography and the first Wolfram Mathematica 12 Full Crack With Activation Key [ 2021] Feistel cipher. DES still remains in many products — and cryptography students and cryptographers will continue to study DES for years to come.

DES Operational Overview

DES uses a 1 Form Proposal - Invoice 1.5 crack serial keygen key. In fact, the 56-bit key is divided into eight 7-bit blocks and an 8th odd parity bit is added to each block (i.e., a "0" or "1" is added to the block so that there are an odd number of 1 bits in each 8-bit block). By using the 8 parity bits for rudimentary error detection, a DES key is actually 64 bits in length for computational purposes although it only has 56 bits worth of randomness, or entropy (See Section A.3 for a brief discussion of entropy and information theory).

FIGURE 11: DES enciphering algorithm.

DES then acts on 64-bit blocks of the plaintext, invoking 16 rounds of permutations, swaps, and substitutes, as shown in Figure 11. The standard includes tables describing all of the selection, permutation, and expansion operations mentioned below; these aspects of the algorithm are not secrets. The basic DES steps are:

  1. The 64-bit block to be encrypted undergoes an initial permutation (IP), where each bit is moved to a new bit position; e.g., the 1st, 2nd, and 3rd bits are moved to the 58th, 50th, and 42nd position, respectively.

  2. The 64-bit permuted input is divided into two 32-bit blocks, called left and right, respectively. The initial values of the left and right blocks are denoted L0 and R0.

  3. There are then 16 rounds of operation on the L and R blocks. During each iteration (where n ranges from 1 to 16), the following formulae apply:

      Ln = Rn-1
      Rn = Ln-1 ⊕ f(Rn-1,Kn)

    At any given step in the process, then, the new L block value is merely taken from the prior R block value. The new R block is calculated by taking the bit-by-bit exclusive-OR (XOR) of the prior L block with the results of applying the DES cipher function, f, to the prior R block and Kn. (Kn is a 48-bit value derived from the 64-bit DES key. Each round uses a different 48 bits according to the standard's Key Schedule algorithm.)

    The cipher function, f, combines the 32-bit R block value and the 48-bit subkey in the following way. First, the 32 bits in the R block are expanded to 48 bits by an expansion function (E); the extra 16 bits are found by repeating the bits in 16 predefined positions. The 48-bit expanded R-block is then ORed with the 48-bit subkey. The result is a 48-bit value that is then divided into eight 6-bit blocks. These are fed as input into 8 selection (S) boxes, denoted S1.,S8. Each 6-bit input yields a 4-bit output using a table lookup based on the 64 possible inputs; this results in a 32-bit output from the S-box. The 32 bits are then rearranged by a permutation function (P), producing the results from the cipher function.

  4. The results from the final DES round — i.e., L16 and R16 — are recombined into a 64-bit value and fed into an inverse initial permutation (IP-1). At this step, the bits are rearranged into their original positions, so that the 58th, 50th, and 42nd bits, for example, are moved back into the 1st, 2nd, and 3rd positions, respectively. The output from IP-1 is the 64-bit ciphertext block.

Consider this example using DES in CBC mode with the following 56-bit key and input:

    Key: 1100101 0100100 1001001 0011101 0110101 0101011 1101100 0011010 = 0x6424491D352B6C1A

    Input character string (ASCII/IA5): +2903015-08091765
    Input string (hex): 0x2B323930333031352D3038303931373635

    Output string (hex): 0x9812CB620B2E9FD3AD90DE2B92C6BBB6C52753AC43E1AFA6
    Output character string (BASE64): mBLLYgsun9OtkN4rksa7tsUnU6xD4a+m

Observe that we start with a 17-byte input message. DES acts on eight bytes at a time, so this message is padded to 24 bytes and provides three "inputs" to the cipher algorithm (we don't see the padding here; it is appended by the DES code). Since we have three input blocks, we get 24 bytes of output from the three 64-bit (eight byte) output blocks.

If you want to test this, a really good free, online DES calculator hosted by the Information Security Group at University RevisionFX REflex v2.3.6 for Adobe After Effects crack serial keygen London. An excellent step-by-step example 1 Form Proposal - Invoice 1.5 crack serial keygen DES can also be found at J. Orlin Grabbe's The DES Algorithm Illustrated page.


NOTE: You'll notice that the output above is shown in BASE64. BASE64 is a 64-character alphabet — i.e., a six-bit character code composed of upper- and lower-case 1 Form Proposal - Invoice 1.5 crack serial keygen, the digits 0-9, and a few punctuation characters — that is commonly used as a way to display binary data. A byte has eight bits, or 256 values, but not all 256 ASCII characters are defined and/or printable. BASE64, simply, takes a binary string (or file), divides it into six-bit blocks, and translates each block into a printable character. More information about BASE64 can be found at my BASE64 Alphabet page or at Wikipedia.

Breaking DES

The mainstream cryptographic community has long held that DES's 56-bit key was too short to withstand a brute-force attack from modern computers. Remember Moore's Law: computer power doubles every 18 months. Given that increase in power, a key that could withstand a brute-force guessing attack in 1975 could hardly be expected to withstand the same attack a quarter century later.

DES is even more vulnerable to a brute-force attack because it is often used to encrypt words, meaning that the entropy of the 64-bit block is, effectively, greatly reduced. That is, if we are encrypting random bit streams, then a given byte might contain any one of 28 (256) possible values and the entire 64-bit block has 264, or about 18.5 quintillion, possible values. If we are encrypting words, however, we are most likely to find a limited set of bit patterns; perhaps 70 or so if we account for upper and lower case letters, the numbers, space, and some punctuation. This means that only about ¼ of the bit combinations of a given byte are likely to occur.

Despite this criticism, the U.S. government insisted throughout the mid-1990s that 56-bit DES was secure and virtually unbreakable if appropriate precautions were taken. In response, RSA Laboratories sponsored a series of cryptographic challenges to prove that DES was no longer appropriate for use.

DES Challenge I was launched in March 1997. It was completed in 84 days by R. Verser in a collaborative effort using thousands of computers on the Internet.

The first DES Challenge II lasted 40 days in early 1998. This problem was solved by distributed.net, a worldwide distributed computing network using the spare CPU cycles of computers around the Internet (participants in distributed.net's activities load a client program that runs in the background, conceptually similar to the SETI @Home "Search for Extraterrestrial Intelligence" project). The distributed.net systems were checking 28 billion keys per second by the end of the project.

The second DES Challenge II lasted less than 3 days. On July 17, 1998, the Electronic Frontier Foundation (EFF) announced the construction of hardware that could brute-force a DES key in an average of 4.5 days. Called Deep Crack, the device could check 90 billion keys per second and cost only about $220,000 including design (it was erroneously and widely reported that subsequent devices could be built for as little as $50,000). Since the design is scalable, this suggests that an organization could build a DES cracker that could break 56-bit keys in an average of a day for as little as $1,000,000. Information about the hardware design and all software can be obtained from the EFF.

The DES Challenge III, launched in January 1999, was broken is less than a day by the combined efforts of Deep Crack and distributed.net. This is widely considered to have been the final nail in DES's coffin.

The Deep Crack algorithm is actually quite interesting. The general approach that the DES Cracker Project took was not to break the algorithm mathematically but instead to launch a brute-force attack by guessing every possible key. A 56-bit key yields 256, or about 72 quadrillion, possible values. So the DES cracker team looked for any shortcuts they could find! First, they assumed that some recognizable plaintext would appear in the decrypted string even though they didn't have a specific known plaintext block. They then applied all 1 Form Proposal - Invoice 1.5 crack serial keygen possible key values to the 64-bit block (I don't mean to make this sound simple!). The system checked to see if the decrypted value of the block was "interesting," which they defined as bytes containing one of the alphanumeric characters, space, or some punctuation. Since the likelihood of a single byte being "interesting" is about ¼, then the likelihood of the entire 8-byte stream being "interesting" is about ¼8, or 1/65536 (½16). This dropped the number of possible keys that might yield positive results to about 240, 1 Form Proposal - Invoice 1.5 crack serial keygen, or about a trillion.

They then made the assumption that an "interesting" 8-byte block would be followed by another "interesting" block. So, if the first block of ciphertext decrypted to something interesting, they decrypted the next block; otherwise, they abandoned this key. Only if the second block was also "interesting" did they examine the key closer. Looking for 16 consecutive bytes that were "interesting" meant that only 224, or 16 million, keys needed to be examined further. This further examination was primarily to see if the text made any sense. Note that possible "interesting" blocks might be 1hJ5&aB7 or DEPOSITS; the latter is more likely to produce a better result, 1 Form Proposal - Invoice 1.5 crack serial keygen. And even a slow laptop today can search through lists of only a few million items in a relatively short period of time. (Interested readers are urged to read Cracking DES and EFF's Cracking DES page.)

It is well beyond the scope of this paper to discuss other forms of breaking DES and other codes. Nevertheless, it is worth mentioning a couple of forms of cryptanalysis that have been shown to be effective against DES. Differential cryptanalysis, invented in 1990 by E. Biham and A. Shamir (of RSA fame), is a chosen-plaintext attack. By selecting pairs of plaintext with particular differences, the cryptanalyst examines the differences in the resultant ciphertext pairs. Linear plaintext, invented by M. Matsui, uses a linear approximation to analyze the actions of a block cipher (including DES). Both of these attacks can be more efficient than brute force.

DES Variants

Once DES was "officially" broken, several variants appeared. But none of them came overnight; work at hardening DES had already been underway. In the early 1990s, there was a proposal to increase the security of DES by effectively increasing the key length by using multiple keys with multiple passes. But for this scheme to work, it had to first be shown that the DES function is not a group, as defined in mathematics. If DES was a group, then we could show that for two DES keys, X1 and X2, applied to some plaintext (P), we can find a single equivalent key, X3, that would provide the same result; i.e.,

EX2(EX1(P)) = EX3(P)

where EX(P) represents DES encryption of some plaintext P using DES key X. If DES were a group, it wouldn't matter how many keys and passes we applied to some plaintext; we could always find a single 56-bit key that would provide the same result.

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Blu-ray

Optical disc format used for storing digital video and other digital data

The Blu-ray Disc (BD), often known simply as Blu-ray, is a digitaloptical discstorage format. It is designed to supersede the DVD format, and capable of storing several hours of high-definition video (HDTV 720p and 1080p). The main application of Blu-ray is as a medium for video material such as feature films and for the physical distribution of video games for the 1 Form Proposal - Invoice 1.5 crack serial keygen 3, PlayStation 4, PlayStation 5, Xbox One, and Xbox Series X. The name "Blu-ray" refers to the blue laser 1 Form Proposal - Invoice 1.5 crack serial keygen is actually a violet laser) used to read the disc, which allows information to be stored at a greater density than is possible with the longer-wavelength red laser used for DVDs.

The plastic disc is 120 millimetres (4.7 in) in diameter and 1.2 millimetres (0.047 in) thick, the same size as DVDs and CDs.[5] Conventional or pre-BD-XL Blu-ray Discs contain 25 GB per layer, with dual-layer discs (50 GB) being the industry standard for feature-length video discs. Triple-layer discs (100 GB) and quadruple-layer discs (128 GB) are available for BD-XL re-writer drives.[6]

High-definition (HD) video may be stored on Blu-ray Discs with up to 1920×1080 pixel resolution, at 24 progressive or 50/60 interlaced frames per second. DVD-Video discs were limited to a maximum resolution of 480i (NTSC, 720×480 pixels) or 576i (PAL, 720×576 pixels).[7] Besides these hardware specifications, Blu-ray is associated with a set of multimedia formats.

The BD format was developed by the Blu-ray Disc Association, a group representing makers of consumer electronics, computer hardware, and motion pictures. Sony unveiled the first Blu-ray Disc prototypes in October 2000, and the first prototype player was released in Japan in April 2003. Afterward, it continued to be developed until its official worldwide release on June 20, 2006, beginning the high-definition optical disc format war, where Blu-ray Disc competed with the HD DVD format. Toshiba, the main company supporting HD DVD, conceded in February 2008,[8] and later released its own Blu-ray Disc player in late 2009.[9] According to Media Research, high-definition software sales in the United States were slower in the first Articulate Storyline 3.12.24693.0 Crack Full Version Free Download years than DVD software sales.[10] Blu-ray faces competition from video on demand (VOD) and the continued sale of DVDs.[11] In January 2016, 44% of U.S. broadband households had a Blu-ray player.[12] For playback of 4K content, the BDA introduced a variant of Blu-ray called Ultra HD Blu-ray.

History[edit]

A blank rewritable Blu-ray Disc (BD-RE)

Early history[edit]

The information density of the DVD format was limited by the wavelength of the laser diodes used. Following protracted development, blue laser diodes operating at 405 nanometers became available on a production basis, allowing for development of a more-dense storage format that could hold higher-definition media, with prototype discs made with diodes at a slightly longer wavelength of 407 nanometers in October 1998.[13][14]Sony started two projects in collaboration with Panasonic, Philips, and TDK,[15] applying the new diodes: UDO (Ultra Density Optical),[16] and DVR Blue (together with Pioneer),[17] a format of rewritable discs that would eventually become Blu-ray Disc (more specifically, BD-RE). The core technologies of the formats are similar. The first DVR Blue prototypes were unveiled by Sony at the CEATEC exhibition in October 2000.[18] A trademark for the "Blue Disc" logo was filed on February 9, 2001.[19] On February 19, 2002, the project was officially announced as Blu-ray Disc,[20][21] and Blu-ray Disc Founders was founded by the nine initial members.

The first consumer device arrived in stores on April 10, 2003: the Sony BDZ-S77, 1 Form Proposal - Invoice 1.5 crack serial keygen, a US$3,800 BD-RE recorder that was made available only in Japan.[22] However, there was no standard for prerecorded video, and no movies were released for this player. Hollywood studios insisted that players be equipped with digital rights management before they would release movies 1 Form Proposal - Invoice 1.5 crack serial keygen the new format, and they wanted a new DRM system that would be more secure than the failed Content Scramble System (CSS) used on Wall Street Explorer v1.13 32-bit crack serial keygen. On October 4, 2004, the name "Blu-ray Disc Founders" was officially changed to the Blu-ray Disc Association (BDA), and 20th Century Fox joined the BDA's Board of Directors.[23] The Blu-ray Disc physical specifications were completed in 2004.[24]

In January 2005, TDK announced that it had developed an ultra-hard yet very thin polymer coating ("Durabis") for Blu-ray Discs; this was a significant technical advance because a far tougher protection was desired in the consumer 1 Form Proposal - Invoice 1.5 crack serial keygen to protect bare discs against scratching and damage compared to DVD, while technically Blu-ray Disc required a much thinner layer for the denser and higher-frequency blue laser.[25] Cartridges, originally used for scratch protection, were no longer necessary and were scrapped. The BD-ROM specifications were finalized in early 2006.[26]

Advanced Access Content System Licensing Administrator (AACS LA), a consortium founded in 2004,[27] had been developing the DRM platform that could be used to securely distribute movies to consumers. However, the final AACS standard was delayed,[28] and then delayed again when an important member of the Blu-ray Disc group voiced concerns.[29] At the request of the initial hardware manufacturers, including Toshiba, Pioneer, and Samsung, an interim standard was published that did not include some features, such as managed copy.[30]

Launch and sales developments[edit]

The first BD-ROM players (Samsung BD-P1000) were shipped in mid-June 2006, though HD DVD players beat them to market by a few months.[31][32] The first Blu-ray Disc titles were released on June 20, 2006: 50 First Dates, The Fifth Element, Hitch, House of Flying Daggers, Underworld: Evolution, xXx (all from Sony), and MGM's The Terminator.[33] The earliest releases used MPEG-2 video compression, the same method used on standard DVDs. The first releases using the newer VC-1 and AVC formats were introduced in September 2006.[34] The first movies using 50 GB dual-layer discs were introduced 1 Form Proposal - Invoice 1.5 crack serial keygen October 2006.[35] The first audio-only albums were released in May 2008.[36][37]

By June 2008, over 2,500 Blu-ray Disc titles were available in Australia and the United Kingdom, with 3,500 in the United States and Canada.[38] In Japan, over 3,300 titles have been released as of July 2010.[39]

Competition from HD DVD[edit]

Main article: High-definition optical disc format war

The DVD Forum, chaired by Toshiba, was split over whether to develop the more expensive blue laser technology, 1 Form Proposal - Invoice 1.5 crack serial keygen. In March 2002 the forum approved a proposal, which was endorsed by Warner Bros. and other motion picture studios. The proposal involved compressing high-definition video onto dual-layer standard DVD-9 discs.[40][41] In spite of this decision, however, the DVD Forum's Steering Committee announced in April that it was pursuing its own blue-laser high-definition video solution. In August, Toshiba and NEC announced their competing standard, the Advanced Optical Disc.[42] It was finally adopted by the DVD Forum and renamed HD DVD the next year,[43] after being voted down twice by DVD Forum members who were also Blu-ray Disc Association members—a situation that drew preliminary investigations by the U.S. Department of Justice.[44]

HD DVD had a head start in the high-definition video market, as Blu-ray Disc sales were slow to gain market share. The first Blu-ray Disc player was perceived as expensive and buggy, and there were few titles available.[45]

The Sony PlayStation 3, which contained a Blu-ray Disc player for primary storage, helped support Blu-ray.[46] Sony also ran a more thorough and influential marketing campaign for the format.[47]AVCHD camcorders were also introduced in 2006. These recordings can be played back on many Blu-ray Disc players without re-encoding but are not compatible with HD DVD players. By January 2007, Blu-ray Discs had outsold HD DVDs,[48] and during the first three quarters of 2007, BD outsold HD DVD by about two to one. At CES 2007, Warner proposed Total Hi Def—a hybrid disc containing Blu-ray on one side and HD DVD on the other, but it was never released.

On June 28, 2007, 20th Century Fox cited Blu-ray Disc's adoption of the BD+ anticopying system as key to their decision to support the Blu-ray Disc format.[49][50] On January 4, 2008, a day before CES 2008, 1 Form Proposal - Invoice 1.5 crack serial keygen, Warner Bros. (the only major studio still releasing movies in both HD DVD and Blu-ray Disc format) announced that it would release only in Blu-ray Disc after May 2008.[51] This effectively included other studios that came under the Warner umbrella, such as New Line Cinema and HBO—though in Europe, HBO's distribution partner, the BBC, announced it would, continue to release product on both formats while keeping an eye on market forces. This led to a chain reaction in the industry, 1 Form Proposal - Invoice 1.5 crack serial keygen, with major American retailers such as 1 Form Proposal - Invoice 1.5 crack serial keygen Buy, Walmart, 1 Form Proposal - Invoice 1.5 crack serial keygen, and Circuit City and Canadian chains such as Future Shop dropping HD DVD in their stores. Woolworths, then a major European retailer, dropped HD DVD from its inventory.[52] Major DVD rental companies Netflix and Blockbuster said they would no longer carry HD DVD, 1 Form Proposal - Invoice 1.5 crack serial keygen.

Following these new developments, on February 19, 2008, Toshiba announced it would end production of HD DVD devices,[53] allowing Blu-ray Disc to become the industry standard for high-density optical discs. Universal Studios, the sole major studio to back HD DVD since its inception, said shortly after Toshiba's announcement: "While Universal values the close partnership we have shared with Toshiba, it is time to turn our focus to releasing new and catalog titles on Blu-ray Disc."[54]Paramount Pictures, which started releasing movies only in HD DVD format during late 2007, also said it would start releasing on Blu-ray Disc. Both studios announced initial Blu-ray lineups in May 2008. With this, all major Hollywood studios supported Blu-ray.[55]

Future scope and market trends[edit]

Ambox current red.svg

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According to Media Research, high-definition software sales in the United States were slower in the first two years than DVD software sales.[10] 16.3 million DVD software units were sold in the first two years (1997–1998) compared to 8.3 million high-definition software units (2006–2007).[10][56] One reason given for this difference was the smaller marketplace (26.5 million HDTVs in 2007 compared to 100 million SDTVs in 1998).[56] Former HD DVD supporter Microsoft did not make a Blu-ray Disc drive for the Xbox 360.[57] The 360's successor Xbox One features a Blu-ray drive, as does the PS4, with both supporting 3D Blu-ray after later firmware updates.[58][59]

Shortly after the "format war" ended, Blu-ray Disc sales began to increase. A study by the NPD Group found that awareness of Blu-ray Disc had reached 60% of households in the United States. Nielsen VideoScan sales numbers showed that for some titles, such as 20th Century Fox's Hitman, up to 14% of total disc 1 Form Proposal - Invoice 1.5 crack serial keygen were from Blu-ray, although the average Blu-ray sales for the first half of the year were only around 5%. In December 2008, the Blu-ray Disc version of Warner Bros.' The Dark Knight sold 600,000 copies on the first day of its launch in the United States, Canada, and the United Kingdom.[60] A week after the launch, The Dark Knight BD had sold over 1.7 million copies worldwide, making it the first Blu-ray Disc title to sell over a million copies in the first week of release.[61]

According to Singulus Technologies AG, Blu-ray was adopted faster than the DVD format was at a similar period in its development, 1 Form Proposal - Invoice 1.5 crack serial keygen. This conclusion was based on the fact that Singulus Technologies received orders for 21 Blu-ray dual-layer replication machines during the first quarter of 2008, while 17 DVD replication machines of this type were made in the same period in 1997.[64] According to GfK Retail and Technology, in the first week of November 2008, sales of Blu-ray recorders surpassed DVD recorders in Japan.[65] According to the Digital Entertainment Group, the number of Blu-ray Disc playback devices (both set-top box and game console) sold in the United States had reached 28.5 million by the end of 2010.[63]

Blu-ray faces competition from video on demand[66] and from new technologies that CSI SAP2000 Ultimate v23.3.0 Build 1756 Crack Full Version Download access to movies on any format or device, such as Digital Entertainment Content Ecosystem or Disney's Keychest.[67] Some commentators suggested that renting Blu-ray would play a vital part in keeping the technology affordable while allowing it to move forward.[68] In an effort to increase sales, studios began releasing films in combo packs with Blu-ray Discs and DVDs, as well as digital copies that can be played on computers and mobile devices. Some are released on "flipper" discs with Blu-ray on one side and DVD on the other. Other strategies are to release movies with the special features only on Blu-ray Discs and none on DVDs.

Blu-ray discs cost no more to produce than DVD discs.[69][70] However, reading and writing mechanisms are more complicated, making Blu-ray recorders, drives and players more expensive than their DVD counterparts.[71][72][73] Adoption is also limited due to the widespread use of streaming media.[74][75][76][77] Blu-ray discs are used to distribute PlayStation 3, PlayStation 4, PlayStation 5, Xbox One and Xbox Series X games, and the aforementioned game consoles can play back regular Blu-ray discs.

Beyond Blu-ray[edit]

Blu-ray case—often blue-colored

Ultra HD Blu-ray discs and players became available in the first quarter of 2016, having a storage capacity of up to 100 GB.[78][79]

The Holographic Versatile Disc (HVD), described in the ECMA-377 standard, has been in development by the Holography System Development (HSD) Forum using a green writing/reading laser (532 nm) and 1 Form Proposal - Invoice 1.5 crack serial keygen red positioning/addressing laser (650 nm). It is to offer MPEG-2, MPEG-4 AVC (H.264), HEVC (H.265), 1 Form Proposal - Invoice 1.5 crack serial keygen, and VC-1 encoding, supporting a maximum storage capacity of 6TB.[80] No systems conforming to the Ecma International HVD standard have been released.[81] SecureCRT 8.5.2 Crack Archives the Blu-ray Disc format is upgradable it poses challenges to the adoption of the HVD format.

Ongoing development[edit]

Ambox current red.svg

This article needs to be updated. Please help update this article to reflect recent events or newly available information.(April 2018)

Front of an experimental 200 GB rewritable Blu-ray Disc

Although the Blu-ray Disc specification has been finalized, engineers continue to work on advancing the technology. By 2005, quad-layer (100 GB)[82] discs had been demonstrated on a drive with modified optics[83] and standard unaltered optics.[84] Hitachi stated that such a disc could be used to store 7 hours of 32 Mbit/s video (HDTV) or 3 hours and 30 minutes of 64 Mbit/s video (ultra-high-definition television). In April 2006, TDK canceled plans to produce 8-layer 200GB Blu-ray Discs.[85] In August 2006, TDK announced that it had created a working experimental Blu-ray Disc capable of holding 200 GB of data on a single side, using six 33 GB data layers.[86] In 2007, Hitachi was reported to have plans to produce 200 GB disks by 2009.[87]

Behind closed doors at CES 2007, Ritek revealed that it 1 Form Proposal - Invoice 1.5 crack serial keygen successfully developed a high-definition optical disc process that extended the disc capacity to ten layers, increasing the capacity of the discs to 250 GB. However, it noted the major obstacle was that current read/write technology did not allow additional layers.[88]JVC developed a three-layer technology that allows putting both standard-definition DVD data and HD data on a BD/(standard) DVD combination.[89] This would have enabled the consumer to purchase a disc that can be played on DVD players and can also reveal its HD version when played on a BD player.[90] Japanese optical disc manufacturer Infinity announced the first "hybrid" Blu-ray Disc/(standard) DVD combo, to be released February 18, 2009. This disc set of the TV series "Code Blue" featured four hybrid discs containing a single Blu-ray Disc layer (25 GB) and two DVD layers (9 GB) on the same side of the disc.[91]

In January 2007, Hitachi showcased a 100 GB Blu-ray Disc, consisting of four layers containing 25 GB each.[92] It claimed that, 1 Form Proposal - Invoice 1.5 crack serial keygen, unlike TDK's and Panasonic's 100 GB discs, this disc would be readable on standard Blu-ray Disc drives that were currently in circulation, and it was believed that a firmware update was the only requirement to make it readable by then-current players and drives.[93] In October 2007 they revealed a 100GB Blu-ray disc drive.[94] In December 2008, Pioneer Corporation unveiled a 400 GB Blu-ray Disc (containing 16 data layers, 25 GB each) compatible with current players after a firmware update. Its planned launch was in the 2009–10 time frame for ROM and 2010–13 for rewritable discs. Ongoing development was underway to create a 1 TB Blu-ray Disc.[95]

At CES 2009, Panasonic unveiled the DMP-B15, the first portable Blu-ray Disc player, and Sharp introduced the LC-BD60U and LC-BD80U series, the first LCD HDTVs with integrated Blu-ray Disc players. Sharp also announced that it would sell HDTVs with integrated Blu-ray Disc recorders in the United States by the end of 2009. Set-top box recorders were not being sold in the U.S. for fear of unauthorized copying. However, personal computers with Blu-ray recorder drives were available. In October 2009, TDK demonstrated a 10-layer 320GB Blu-ray disc.[96] On January 1, 2010, Sony, in association with Panasonic, announced plans to increase the storage capacity on their Blu-ray Discs from 25 GB to 33.4 GB via a technology called i-MLSE (Maximum likelihood Sequence Estimation). The higher-capacity discs, according to Sony, would be readable on existing Blu-ray Disc players with a firmware upgrade.[97] This technology was later used on BDXL discs.[98]

On July 20, 2010, the research team of Sony and Japanese Tohoku University announced the joint development of a blue-violet laser,[99] to help create Blu-ray Discs with a capacity of 1 TB using only two layers (and potentially more than 1 TB with additional layering). By comparison, the first blue laser was invented in 1996, with the first prototype discs coming four years later.

Resharper 2019.3 activation key Archives src="https://upload.wikimedia.org/wikipedia/commons/thumb/8/8c/4K_Blu_Ray_early_Best_Buy_release.jpg/220px-4K_Blu_Ray_early_Best_Buy_release.jpg" width="220" height="146">
Early 4K Blu-ray release at Best Buy. A 4K Blu-ray Disc player was also released.

On January 7, 2013, Sony announced that it would release "Mastered in 4K" Blu-ray Disc titles sourced at 4K and encoded at 1080p.[100] "Mastered in 4K" Blu-ray Disc titles can be played on existing Blu-ray Disc players and have a larger color space using xvYCC.[100][101] On January 14, 2013, Blu-ray Disc Association president Andy Parsons stated that a task force was created three months prior to conduct a study concerning an extension to the Blu-ray Disc specification that would add the ability to contain 4K Ultra HD video.[102][103]

On August 5, 2015, the Blu-ray Disc Association (BDA) announced it would commence licensing the Ultra HD Blu-ray format starting on August 24, 2015. The Ultra HD Blu-ray format delivered high dynamic range content that significantly expanded the range between the brightest and darkest elements, expanded color range, high frame rate (up to 60fps) and up to 3840×2160 resolution, object-based sound formats, and an optional "digital bridge" feature. New players were required to play this format, which were able to play both DVDs, traditional Blu-rays and the new format. New Ultra HD Blu-ray Discs hold up to 66 GB and 100 GB of data on dual- and triple-layer discs, respectively.[104]

Blu-ray's physical and file system specifications are publicly available on the Blu-ray disc association's website.[105]

Physical media[edit]

Comparison of several forms of disc storage showing tracks (not to scale); green denotes start and red denotes end.
* Some CD-R(W) and 1 Form Proposal - Invoice 1.5 crack serial keygen recorders operate in ZCLV, CAA or CAV modes.
Comparison of various optical storage media
Type Diameter
(cm)
Layers Capacity
Bytes
Standard disc size, single layer12125,025,314,816
Standard disc size, dual layer12250,050,629,632
Standard disc size, XL 3 layer[106]123100,103,356,416
Standard disc size, XL 4 layer[106]124128,001,769,472
Mini disc size, single layer817,791,181,824
Mini disc size, 1 Form Proposal - Invoice 1.5 crack serial keygen, dual layer8215,582,363,648

Laser and optics[edit]

While a DVD uses a 650 nm red laser, Blu-ray Disc uses a 405 nm "blue" laser CCleaner 5.09.5343 crack serial keygen. Although the laser is called "blue", its color is actually in the violet range. The shorter wavelength can be focused to a smaller area, thus enabling it to read information recorded in pits that are less than half the size of those on a DVD, and can consequently be spaced more closely, resulting in a shorter track pitch, enabling a Blu-ray Disc to hold about five times the amount of information that can be stored on a DVD. The lasers are GaN (gallium nitride) laser diodes that produce 405 nm light directly, that is, without frequency doubling or other nonlinear optical mechanisms.[107][14]CDs use 780 nm near-infrared lasers.

The minimum "spot size" on which a laser can be focused is limited by diffraction and depends on the wavelength of the light and the numerical aperture of the lens used to focus it. By decreasing the wavelength, increasing the numerical aperture from 0.60 to 0.85, 1 Form Proposal - Invoice 1.5 crack serial keygen, and making the cover layer thinner to avoid unwanted optical effects, designers can cause the laser beam to focus on a smaller spot, which effectively allows more information to be stored in the same area.[108] For a Blu-ray Disc, the spot size is 580 nm.[109] This allows a reduction of the pit size from 400 nm for DVD to 150 nm for Blu-ray Disc, and of the track pitch from 740 nm to 320 nm.[108] See compact disc for information on optical discs' physical structure. In addition to the optical improvements, Blu-ray Discs feature improvements in data encoding that further increase the amount of content that can be stored.[110]

Hard-coating technology[edit]

Given that the Blu-ray Disc data layer is closer to the surface of the disc compared to the DVD standard, it was found in early designs to be more vulnerable to scratches.[111][112] The first discs were therefore housed in cartridges for protection, resembling Professional Discs introduced by Sony in 2003. Using a cartridge would increase the price of an already expensive medium, and would increase the size of Blu-ray disc drives, so designers chose hard-coating of the pickup surface instead. TDK was the first company to develop a working scratch-protection coating for Blu-ray Discs, naming it Durabis. In addition, both Sony's and Panasonic's replication methods include proprietary hard-coat technologies. Sony's rewritable media are spin-coated, using a scratch-resistant acrylic and antistatic coating.[113]Verbatim's recordable and rewritable Blu-ray Discs use their own proprietary technology, called Hard Coat.[114] Colloidal silica-dispersed UV-curable resins are used for the hard coating, given that, according to the Blu-ray Disc Association, they offer the best tradeoff between scratch resistance, optical properties, and productivity.[113]

The Blu-ray Disc specification requires the testing of resistance to scratches by mechanical abrasion.[108] In contrast, DVD media are not required to be scratch-resistant, but since development of the technology, some companies, such as Pc cleaner pro crack serial keygen, implemented hard-coating for more expensive lines of recordable DVDs.

Drive speeds[edit]

Drive speed Data rate ~Write time (minutes) ~CAV Rotation speed (RPM)[115]
Mbit/sMB/sSingle-LayerDual-Layer
364.590180810
72945901,620
1441822.5453,240
2162715304,860
2883611.2522.56,480
10×360459188,100
12× 432547.5159,720
14× 504636.51311,340
16× 576725.711.512,960

The table shows the speeds available. Even the lowest speed (1×) is sufficient to play and record real-time 1080p video; the higher speeds are relevant for general data storage and more sophisticated handling of video. BD discs are designed to cope with at least 5,000rpm of rotational speed.

The usable data rate of a Blu-ray Disc drive can be limited by the capacity of the drive's data interface. With a USB 2.0 interface, the maximum exploitable drive speed is 288 Mbit/s or 36 MB/s (also called 8× speed).[116] A USB 3.0 interface (with proper cabling) does not have this limitation,[117] nor do even the oldest version of Serial ATA (SATA, 150 MB/s)[118] nor the latest Parallel ATA (133 MB/s) standards. Internal Blu-ray drives that are integrated into a computer (as opposed to physically separate and connected via a cable) typically have a SATA interface.[119]

More recent half-height Blu-Ray writers have 1 Form Proposal - Invoice 1.5 crack serial keygen writing speeds of up to 16× (constant angular velocity) on single-layer BD-R media, while the highest reading speeds are 12×, presumably to prevent repeated physical stress on the disc. Slim type drives are limited to 6× speeds (constant angular velocity) due to spacial and power limitations.[120][121][122]

Media quality and data integrity[edit]

Main article: Optical disc § Surface error scanning

The quality and data integrity of optical media can be determined by measuring the rate of errors, of which higher rates may be an indication for deteriorating media, low-quality media, physical damage such as scratches, dust, and/or media written using a defective optical drive.

Errors on Blu-Ray media is measured using the so-called LDC (Long Distance Codes) and BIS (Burst Indication Subcodes) error parameters, of which rates below 13 and 15 respectively can be considered healthy.

Not all vendors and models of optical drives have error scanning functionality implemented.[123][124][14]

Packaging[edit]

Pre-recorded Blu-ray Disc titles usually ship in packages similar to but slightly smaller (18.5 mm shorter and 2 mm thinner: 135 mm × 171.5 mm × 13 mm[125]), as well as more rounded than a standard DVDkeep case, generally with the format prominently displayed in a horizontal stripe across the top of the case (translucent blue for Blu-ray video discs, clear for Blu-ray 3D video releases, red for PlayStation 3 Greatest Hits Games, transparent for regular PlayStation 3 games, transparent dark blue for PlayStation 4 and PlayStation 5 games, transparent green for Xbox One and Xbox Series X games and black for Ultra HD Blu-ray video releases). Warren Osborn and The Seastone Media Group, LLC created the package that was adopted worldwide following the Blu-ray versus HD DVD market adoption choice.[126] Because Blu-ray cases are smaller than DVD cases, more Blu-rays than DVDs can fit on a shelf.

Types[edit]

Mini Blu-ray Disc[edit]

The "Mini Blu-ray Disc" (also, "Mini-BD" and "Mini Blu-ray") is a compact 8-centimetre-diameter (3.1 in) variant of the Blu-ray Disc that can store 7.8 GB of data in its single-layer configuration, or 15.6 GB on a dual-layer disc.[127] It is similar in concept to the MiniDVD and MiniCD. Recordable (BD-R) and rewritable (BD-RE) versions of Mini Blu-ray Disc have been developed specifically for compact camcorders and other compact recording devices.[128]

Blu-ray Disc recordable[edit]

Main article: Blu-ray Disc recordable

"Blu-ray Disc recordable" (BD-R) refers to two optical disc formats that can be recorded with an optical disc recorder. BD-Rs can be written to once, whereas Blu-ray Disc Recordable Erasable (BD-REs) can be erased and re-recorded multiple times. The current practical maximum speed for Blu-ray Discs is about 12× (54 MB/s).[129]: 1.7  Higher speeds of rotation (5,000+ rpm[113]) cause too much wobble for the discs to be written properly,[130][131] as with the 24× (33.2 MB/s) and 56× (8.2 MB/s, 11,200 rpm) maximum speeds, respectively, of standard DVDs and CDs. Since September 2007, BD-RE is also available in the smaller 8 cm Mini Blu-ray Disc size.[128][132]

On September 18, 2007, Pioneer and Mitsubishi codeveloped BD-R LTH ("Low to High" in groove recording), which features an organic dye recording layer that can be manufactured by modifying existing CD-R and DVD-R production equipment, significantly reducing manufacturing costs.[133] In February 2008, 1 Form Proposal - Invoice 1.5 crack serial keygen, Taiyo Yuden, Mitsubishi, and Maxell released the first BD-R LTH Discs,[134] and in March 2008, Sony's PlayStation 3 officially gained the ability to use BD-R LTH Discs with the 2.20 firmware update.[135] In May 2009 Verbatim/Mitsubishi announced the industry's first 6X BD-R LTH media, which allows recording a 25 GB disc in about 16 minutes.[136] Unlike with the previous releases of 120 mm optical discs (i.e. CDs and standard DVDs), Blu-ray recorders hit the market almost simultaneously with Blu-ray's debut.

BD9 and BD5[edit]

The BD9 format was proposed to the Blu-ray Disc Association by Warner Home Video as a cost-effective alternative to the 25/50 GB BD-ROM discs. The format was supposed to use the same codecs and program structure as Blu-ray Disc video but recorded 1 Form Proposal - Invoice 1.5 crack serial keygen less expensive 8.5 GB dual-layer DVD. This red-laser media could be manufactured on existing DVD production lines with lower costs of production than the 25/50 GB Blu-ray media.[137]

Usage of BD9 for releasing content on "pressed" discs never caught on. With the end of the format war, manufacturers ramped production of Blu-ray Discs and lowered prices to compete with DVDs. On the other hand, the idea of using inexpensive DVD media became popular among individual users. A lower-capacity version of this format that uses single-layer 4.7 GB DVDs has been unofficially called BD5. Both formats are being used by individuals for recording high-definition content in Blu-ray format onto recordable DVD media.[138][139] Despite the fact that the BD9 format has been adopted as part of the BD-ROM basic format, 1 Form Proposal - Invoice 1.5 crack serial keygen, none of the existing Blu-ray player models explicitly claim to be able to read it. Consequently, the discs recorded in BD9 and BD5 formats are not guaranteed to play on standard Blu-ray Disc players. AVCHD and AVCREC also use inexpensive media like DVDs, but unlike BD9 and BD5 these formats have limited interactivity, codec types, and data rates. As of March 2011, BD9 was removed as an official BD-ROM disc.[140]

BDXL[edit]

Grounded v0.2.2 PC full crack - Free Download - Repack - Hiu Games src="https://upload.wikimedia.org/wikipedia/commons/thumb/b/b7/SHARP_BD-XL_100GB_TRIPLE_LAYER.jpg/220px-SHARP_BD-XL_100GB_TRIPLE_LAYER.jpg" width="220" height="222">
100 GB BDXL triple-layer disc by Sharp

The BDXL format allows 100 GB and 128 GB write-once discs,[141][142] and 100 GB rewritable discs for commercial applications. The BDXL specification was finalised in June 2010 but the first 128 GB quad-layer discs were not released until November 2018, and these discs are currently sold only in Japan.[143][144] BD-R 3.0 Format Specification (BDXL) defined a multi-layered disc recordable in BDAV format with the speed of 2× and 4×, capable of 100/128 GB and usage of UDF2.5/2.6.[145] BD-RE 4.0 Format Specification (BDXL) defined a multi-layered disc rewritable in BDAV with the speed of 2× and 4×, capable of 100 GB and usage of UDF2.5 as file 1 Form Proposal - Invoice 1.5 crack serial keygen Although the 66 GB and 100 GB BD-ROM discs used for Ultra HD Blu-ray use the same linear density as BDXL, the two formats are not compatible with each other, therefore it is not possible to use a triple layer BDXL disc to burn an Ultra HD Blu-ray disc playable in an Ultra HD Blu-ray player.

IH-BD[edit]

The IH-BD (Intra-Hybrid Blu-ray) format includes a 25 GB rewritable layer (BD-RE) and a 25 GB write-once layer (BD-ROM), designed to work with existing Blu-ray Discs.[141][142]

Data format standards[edit]

Filesystem[edit]

Blu-ray Disc specifies the use of Universal Disk Format (UDF) 2.50 as a convergent-friendly format for both PC and consumer electronics environments. It is used in the latest specifications Speedify 10.4.1 Crack Archives BD-ROM, BD-RE, and BD-R.[147][148][149] In the first BD-RE specification (defined in 2002), the BDFS (Blu-ray Disc File System) was used. The BD-RE 1.0 specification was defined mainly for the digital recording of high-definition television (HDTV) broadcast television. The BDFS was replaced by UDF 2.50 in the second BD-RE specification in 2005, in order to enable interoperability among consumer electronics Blu-ray recorders and personal computer systems. These optical disc recording technologies enabled PC recording and playback of BD-RE.[149][150][151] BD-R can use UDF 2.50/2.60.[152]

The Blu-ray Disc application for recording of digital broadcasting has been developed as System Description Blu-ray Rewritable Disc Format part 3 Audio Visual Basic Specifications (BDAV). The requirements related with computer file system have been specified in System Description Blu-ray Rewritable Disc Format part 2 File System Specifications version 1.0 (BDFS).[153] Initially, 1 Form Proposal - Invoice 1.5 crack serial keygen, the BD-RE version 1.0 (BDFS) was specifically developed for recording of digital broadcasts using the Blu-ray Disc application (BDAV application). But these requirements are superseded by the Blu-ray Rewritable Disc File System Specifications version 2.0 (UDF) (a.k.a, 1 Form Proposal - Invoice 1.5 crack serial keygen. RE 2.0) and Blu-ray Recordable Disc File System Specifications version 1.0 (UDF) (a.k.a. R 1.0). Additionally, a new application format, BDMV (System Description Blu-ray Disc Prerecorded Format part 3 Audio Visual Basic Specifications) for High Definition Content Distribution was developed for BD-ROM. The only file system developed for BDMV is the System 1 Form Proposal - Invoice 1.5 crack serial keygen Blu-ray Read-Only Disc Format part 2 File System Specifications version 1.0 (UDF) which defines the requirements for UDF 2.50.[149][153]

Application format[edit]

Directory and file structure[edit]

All BDMV application files are stored under a "BDMV" directory.[158][159][160][161]

  • BDMV directory: contains the PLAYLIST, CLIPINF, STREAM, AUXDATA and BACKUP 1 Form Proposal - Invoice 1.5 crack serial keygen.
    • PLAYLIST directory: contains the Database files for Movie PlayLists.
      • xxxxx.mpls files: store information corresponding to Movie PlayLists. One file is created for each Movie PlayList. The filenames of these files are in the form "xxxxx.mpls", where "xxxxx" is a 5-digit number corresponding to the Movie PlayList.
    • CLIPINF directory: contains the Database files for Clips.
      • zzzzz.clpi files: store Clip information associated with a Clip AV stream file. The filenames of these files are in the form "zzzzz.clpi", where "zzzzz" is a 5-digit number corresponding to the Clip.
    • STREAM directory: contains AV stream files.
      • zzzzz.m2ts file: contains a BDAV MPEG-2 transport stream. The names of these files are in the form "zzzzz.m2ts", where "zzzzz" is a 5-digit number corresponding to the Clip. The same 5-digit number "zzzzz" is used for an AV stream file and its associated Clip information file.
      • SSIF directory: If used, Stereoscopic Interleaved files shall be placed under this directory, 1 Form Proposal - Invoice 1.5 crack serial keygen.
        • zzzzz.ssif file: is a Stereoscopic Interleaved file that is composed from two BDAV MPEG-2 transport streams. Both of the streams include an MPEG-4 MVC view video stream for left eye or right eye respectively. This file is used only when 3D video is played back. The 5-digit number "zzzzz" is the same as the number used for the AV stream file "zzzzz.m2ts" that includes the MPEG-4 MVC Base view video stream.
    • AUXDATA directory: contains Sound data files and Font files.
      • sound.bdmv file: stores data relating to one or more sounds associated with HDMV Interactive Graphic streams applications. This file may or may not exist under the AUXDATA directory. If it exists, there shall be only one sound.bdmv file.
      • aaaaa.otf file: stores the font information associated with Text 1 Form Proposal - Invoice 1.5 crack serial keygen applications. The names of these files are in the form "aaaaa.otf", where "aaaaa" is a 5-digit number corresponding to the Font.
    • BACKUP directory: contains copies of the "index.bdmv" file, the "MovieObject.bdmv" file, all the files in the PLAYLIST directory and all files in the CLIPINF directory.
    • index.bdmv file: stores information describing the contents of the BDMV directory. There is only one index.bdmv file under the BDMV directory.
    • MovieObject.bdmv file: stores information for one or more Navicat discount Archives - Patch Cracks Objects. There is only one MovieObject.bdmv under the BDMV directory.

Media format[edit]

Container format[edit]

Audio, video, 1 Form Proposal - Invoice 1.5 crack serial keygen, and other streams are multiplexed and stored on Blu-ray Discs in a container format based on the MPEG transport stream. It is also known as BDAV MPEG-2 transport stream and can use filename extension .m2ts.[158][162] Blu-ray Disc titles authored with menus are in the BDMV (Blu-ray Disc Movie) format and contain audio, video, and other streams in BDAV container.[163][164] There is also the BDAV (Blu-ray Disc Audio/Visual) format, the consumer oriented alternative to the BDMV format used for movie releases. The BDAV format is used on BD-REs and BD-Rs for audio/video recording.[164] BDMV format was later defined also for BD-RE and BD-R (in September 2006, in the third revision of BD-RE specification and second revision of BD-R specification).[147][148]

Blu-ray Disc employs the MPEG transport stream recording method. That enables transport streams of digital broadcasts to be recorded as they are broadcast, without altering the format.[165] It also enables flexible editing of a digital broadcast that is recorded as is and where the data can be edited just by rewriting the playback stream. Although it is quite natural, a function for high-speed and easy-to-use retrieval is built in.[165][166] Blu-ray Disc Video use MPEG transport streams, compared to DVD's MPEG program streams. An MPEG transport stream contains one or more MPEG program streams, so this allows multiple video programs to be stored in the same file so they can be played back simultaneously (e.g. with "picture-in-picture" effect).

Codecs[edit]

The BD-ROM specification mandates certain codec compatibilities for both hardware decoders (players) and movie software (content).[162][167]Windows Media Player does not come with the codecs required to play Blu-ray Discs.[168]

Video[edit]

Originally, BD-ROMs stored video up to 1920×1080 pixel resolution at up to 60 (59.94) fields per second. Currently, with UHD BD-ROM, videos can be stored at a maximum of 3840×2160 pixel resolution at up to 60 (59.94) frames per second, progressively scanned. While most current Blu-ray players and recorders can 1 Form Proposal - Invoice 1.5 crack serial keygen and write 1920×1080 video at the full 59.94p and 50p progressive format, new players for the UHD specifications will be able to read at 3840×2160 video at either 59.94p and 50p formats.

FormatResolution and
frame rate
Display aspect ratio
4K UHD[a]3840×2160 60p16:9
3840×2160 59.94p16:9
3840×2160 50p16:9
3840×2160 25p16:9
3840×2160 24p16:9
3840×2160 23.976p16:9
HD[a]1920×1080 60p16:9
1920×1080 59.94p16:9
1920×1080 50p16:9
1920×1080 25p16:9
HD 1920×1080 29.97i16:9
1920×1080 25i16:9
1920×1080 24p16:9
1920×1080 23.976p16:9
1440×1080 29.97i[b]16:9[c]
1440×1080 25i[b]16:9[c]
1440×1080 24p[b]16:9[c]
1440×1080 23.976p[b]16:9[c]
1280×720 59.94p16:9
1280×720 50p16:9
1280×720 24p16:9
1280×720 23.976p16:9
SD 720×480 29.97i4:3 or 16:9[c]
720×576 25i4:3 or 16:9[c]

^ a Only supported on UltraHD Blu-ray with HEVC video compression standard.
^ b MPEG-2 at 1440×1080 was previously not included in a draft version of the specification from March 2005.[171]
^ c These resolutions are stored anamorphically, i.e. they are stretched to the display aspect ratio by the player or display.

For video, all players are required to Vehicle Simulator v1.5 Car and Truck Edition crack serial keygen H.262/MPEG-2 Part 2, H.264/MPEG-4 Part 10: AVC, and SMPTEVC-1.[172] BD-ROM titles with video must store video using one of the three mandatory formats; multiple formats on a single title are allowed. Blu-ray Disc allows video with a bit depth of 8-bits per color YCbCr with 4:2:0 chroma subsampling.[173][174] The choice of formats affects the producer's licensing/royalty costs as well as the title's maximum run time, due to differences in compression efficiency. Discs encoded in MPEG-2 video typically limit content producers to around two hours of high-definition content on a single-layer (25 GB) BD-ROM. The more-advanced video formats (VC-1 and MPEG-4 AVC) typically achieve a video run time twice that of MPEG-2, with comparable quality.

MPEG-2 was used by many studios (including Paramount Pictures, which initially used the VC-1 format for HD DVD releases) for the first series of Blu-ray Discs, which were launched throughout 2006.[175] Modern releases are now often encoded in either MPEG-4 AVC or VC-1, allowing film studios to place all content on 1 Form Proposal - Invoice 1.5 crack serial keygen disc, reducing costs and improving ease of use. Using these formats also frees a lot of space for storage of bonus content in HD (1080i/p), as opposed to the SD (480i/p) typically used for most titles. Some studios, such as Warner Bros., have released bonus content on discs encoded in a different format than the main feature title. For example, the Blu-ray Disc release of Superman Returns uses VC-1 for the feature film and MPEG-2 for some of its bonus content.[176] Today[when?], Warner and other studios typically provide bonus content in the video format that matches the feature.[citation needed]

Audio[edit]

For audio, BD-ROM players are required to implement Dolby Digital (AC-3), DTS, and linear PCM. Players may optionally implement Dolby Digital Plus and DTS-HD High Resolution Audio as well as lossless formats Dolby TrueHD and DTS-HD Master Audio.[177] BD-ROM titles must use one of the mandatory schemes for the primary soundtrack. A secondary audiotrack, if present, may use any of the mandatory or optional codecs.[citation needed]

LPCM (uncompressed)Dolby DigitalDolby Digital PlusDolby TrueHD (lossless)DTS Digital SurroundDTS-HD Master Audio (lossless)DRADRA extension
Max. bitrate27.648 Mbit/s640 kbit/s4.736 Mbit/s18.64 Mbit/s1.524 Mbit/s24.5 Mbit/s1.5 Mbit/s3.0 Mbit/s
Max. channel8 (48 kHz, 96 kHz), 6 (192 kHz)5.17.18 (48 kHz, 96 kHz), 6 (192 kHz)5.18 (48 kHz, 96 kHz), 6 (192 kHz)5.17.1
Bits/sample16, 20, 2416, 2416, 2416, 2416, 20, 2416, 241616
Sample frequency48 kHz, 96 kHz, 192 kHz48 kHz48 kHz48 kHz, 96 kHz, 192 kHz48 kHz48 kHz, 96 kHz, 192 kHz48 kHz48 kHz, 96 kHz

Bit rate[edit]

For users recording digital television programming, the recordable Blu-ray Disc standard's initial data rate of 36 Mbit/s is more than adequate to record high-definition broadcasts from any source (IPTV, cable/satellite, or terrestrial). BD Video movies have a maximum data transfer rate of 54 Mbit/s, a maximum AV bitrate of 48 Mbit/s (for both audio and video data), and a maximum video bit rate of 40 Mbit/s. This compares to HD DVD movies, which have a maximum data transfer rate of 36 Mbit/s, a maximum AV bitrate of 30.24 Mbit/s, and a maximum video bitrate of 29.4 Mbit/s.[179]

Java software interface[edit]

Main article: BD-J

At the 2005 JavaOne trade show, it was announced that Sun Microsystems' Java cross-platform software environment would be included in all Blu-ray Disc players as a mandatory part of the standard.[180] Java is used to implement interactive menus on Blu-ray Discs, as opposed to the method used on DVD-video discs. DVDs use pre-rendered MPEG segments and selectable subtitle pictures, which are considerably more primitive and rarely seamless. At the conference, Java creator James Gosling suggested that the inclusion of a Java virtual machine, as well as network connectivity in some BD devices, will allow updates to Blu-ray Discs via the Internet, adding content such as additional subtitle languages and promotional features not included on the disc at pressing time.[181] This Java Version is called BD-J and is built on a profile of the Globally Executable MHP (GEM) standard; GEM is the worldwide version of the Multimedia Home Platform standard.[citation needed]

Player profiles[edit]

The BD-ROM specification defines four Blu-ray Disc player profiles, including an audio-only player profile (BD-Audio) that does not require video decoding or BD-J. All of the video-based player profiles (BD-Video) are required to have a full implementation of BD-J.[citation needed]

Feature BD-Audio BD-Video
Grace Period[d]Bonus ViewBD-Live[e]Blu-ray 3D
Profile 3.0[c]Profile 1.0 Profile 1.1 Profile 2.0 Profile 5.0
Built-in persistent memory Unneeded 64 KB 64 KB 64 KB 64 KB?
Local storage capability[a]Unneeded Optional 256 MB 1 GB 1 GB
Secondary video decoder (PiP) No videoOptional Mandatory Mandatory Mandatory
Secondary audio decoder[b]Optional Optional Mandatory Mandatory Mandatory
Virtual file systemUnneeded Optional Mandatory Mandatory Mandatory
Internet connection capability No No No Mandatory Mandatory

^ a This is used for storing audio/video and title updates. It can either be built-in memory or removable media, such as a memory card or USB flash memory.
^ b A secondary audio decoder is typically used for interactive audio and commentary.
^ c Profile 3.0 is a separate audio-only player profile. The first Blu-ray Disc album to be released was Divertimenti, by record label Lindberg Lyd, and it has been confirmed to work on the PS3.[182][183]
^ d Also known as Initial Standard profile.
^ e Also known as Final Standard profile.

On November 2, 2007, the Grace Period Profile was superseded by Bonus View as the minimum profile for new BD-Video players released to the market.[184] When Blu-ray Disc software not authored with interactive features dependent on Bonus View or BD-Live hardware capabilities is played on Profile 1.0 players, it is able to play the main feature of the disc, but some extra features may not be available or will have limited capability.[185]

BD-Live[edit]

The biggest difference between Bonus View and BD-Live is that BD-Live requires the Blu-ray Disc player to have an Internet connection to access Internet-based content. BD-Live features have included Internet chats, scheduled chats with the director, Internet games, downloadable featurettes, downloadable quizzes, and downloadable movie trailers.[186][187][188] While some Bonus View players may have an Ethernet port, it is used for firmware updates and is not used for Internet-based content.[189] In addition, Profile 2.0 also requires more local storage in order to handle this content.[citation needed]

Profile 1.0 players are not eligible for Bonus View or BD-Live compliant upgrades and do not have the function or capability to access these upgrades, with the exception of the latest players and the PlayStation 3. Internet is required to use.[190][191][192]

Region codes[edit]

Regions for the Blu-ray Disc standard:[193]

  Region A/1

  Region B/2

  Region C/3

As with the implementation of region codes for DVDs, Blu-ray Disc players sold in a specific geographical region are designed to play only discs authorized by the content provider for that region. This is intended to permit content providers (motion picture studios, television production company etc.) to enact regional price discrimination and/or exclusivecontent licensing. According to the Blu-ray Disc Association, all Blu-ray Disc players and Blu-ray Disc-equipped computer systems are required to enforce regional coding. However, content providers need not use region playback codes.[194] Some current estimates suggest 70% of available movie Blu-ray Discs from the major studios are region-free and can therefore be played on any Blu-ray Disc player in any region.[195]

Movie distributors have different region coding policies. Among major U.S. studios, Walt Disney Pictures, Warner Bros., Paramount Pictures, Universal Studios, and Sony Pictures have released most of their titles free of region coding.[196][197][198][199][200][201]MGM and Lions Gate Entertainment have released a mix of region-free and region-coded titles.[202][203]20th Century Fox released most of their titles region-coded pre-Disney merger.[204] Most of their post-Disney merger content is region-free, however. Vintage film restoration and distribution company The Criterion Collection uses US region coding in all Blu-ray releases, with their releases in the UK market using UK region coding.[205][206]

The Blu-ray Disc region coding scheme divides the world into three regions, labeled A, B, 1 Form Proposal - Invoice 1.5 crack serial keygen, and C.

Region Area
AAmericas, Hong Kong SAR, Japan, North Korea, South Korea, Macau SAR, Singapore, Taiwan, Oceania excluding Australia and New Zealand, Southeast Asia.
BAfrica, Middle East, Southwest Asia, most of Europe (excluding Belarus, Russia, Ukraine, Moldova), Australia, New Zealand.
CCentral Asia, mainland China, Mongolia, Indian subcontinent, Belarus, Russia, Ukraine, Kazakhstan, Moldova.
FREEInformal term meaning "worldwide". Region free is not an official setting; discs that bear the region FREE symbol either have no flags set or have all three flags set. Discs with no flags set may not play in some non-compliant players.
A/B/C

A new form of Blu-ray region coding tests not only the region of the player/player software, but also its country code[citation needed], repurposing a user setting intended for localization (PSR19) as a new form of regional lockout. This means, for example, while both the US and Japan are Region A, some American discs will not play on devices/software configured for Japan or vice versa, since the two countries have different country codes. (For example, the United States is "US" (21843 or hex 0x5553), Japan is "JP" (19024 or hex 0x4a50), and Canada is "CA" (17217 or hex 0x4341).[citation needed]) Although there are only three Blu-ray regions, the country code allows much more precise control of the regional distribution of Blu-ray Discs than the six (or eight) DVD regions. With 1 Form Proposal - Invoice 1.5 crack serial keygen Discs, there are no "special regions" such as the regions 7 and 8 for DVDs.

In circumvention of region coding restrictions, stand-alone Blu-ray Disc 1 Form Proposal - Invoice 1.5 crack serial keygen are sometimes modified by third parties to allow for playback of Blu-ray Discs (and DVDs) with any region code.[207] Instructions ("hacks") describing how to reset the Blu-ray region counter of computer player applications to make them multi-region indefinitely are also regularly posted to video enthusiast websites and forums. Unlike DVD region codes, Blu-ray region codes are verified only by the player software, not by the optical drive's firmware.

The latest types of Blu-ray players, suitable for UltraHD content, are not region-free; however; the UHD discs for which they are designed have not been coded to be locked to any region, and will work worldwide.[208]

Digital rights management[edit]

The Blu-ray Disc format employs several layers of digital rights management (DRM) which restrict the usage of the discs.[209][210] This has led to extensive criticism of the format by organizations opposed to DRM, such as the Free Software Foundation,[211] and consumers because new releases require player firmware updates to allow disc playback.[212][213]

High-bandwidth Digital Content Protection[edit]

Main article: High-bandwidth Digital Content Protection

Blu-ray equipment is required to implement the High-bandwidth Digital Content Protection (HDCP) system to encrypt the data sent by players to rendering devices through physical connections. This is aimed at preventing the copying of copyrighted content as it travels across cables. Through a protocol flag in the media stream called the Image Constraint Token (ICT), a Blu-ray Disc can enforce its reproduction in a lower resolution whenever a full HDCP-compliant link is not used. In order to ease the transition to high definition formats, the adoption of this protection method was postponed until 2011.[214]

Advanced Access Content System[edit]

Main article: Advanced Access Content System

The AACS decryption process

The Advanced Access Content System (AACS) is a standard for content distribution and digital rights management. It was developed by AS Licensing Administrator, LLC (AACS LA), a consortium that includes Disney, Intel, Microsoft, Panasonic, Warner Bros., IBM, Toshiba, and Sony. Since the appearance of the format on devices in 2006, several successful attacks have been made on it. The first known attack relied on the trusted client problem. In addition, decryption keys have been extracted from a weakly protected 1 Form Proposal - Invoice 1.5 crack serial keygen (WinDVD). Since keys can be revoked in newer releases,[215] this is only a temporary attack, and new keys must continually 1 Form Proposal - Invoice 1.5 crack serial keygen discovered in order to decrypt the latest discs.[citation needed]

BD+[edit]

Main article: BD+

BD+ was developed by Cryptography Research Inc. and is based on their concept of Self-Protecting Digital Content.[216] BD+, effectively a small Dr.Fone 9.9.2 serial key Archives machine embedded in authorized players, allows content providers to include executable programs on Blu-ray Discs. Such programs can:[209]

  • Examine the host environment to see if the player has been tampered with. Every licensed playback device manufacturer must provide the BD+ licensing authority with memory footprints that identify their devices.
  • Verify that the player's keys have not been changed
  • Execute native code, possibly to patch an otherwise insecure system
  • Transform the audio and video output. Parts of the content will not be viewable without letting the BD+ program unscramble it.

If a playback device manufacturer finds that its devices have been hacked, it can potentially release BD+ code that detects and circumvents the vulnerability. These programs 1 Form Proposal - Invoice 1.5 crack serial keygen then be included in all new content releases.[217] The specifications of the BD+ virtual machine are available only to licensed device manufacturers. A list of licensed commercial adopters is available from the BD+ website.

The first titles using BD+ were released in October 2007. Since November 2007, versions of BD+ protection have been circumvented by various versions of the AnyDVD HD program.[218][219] Other programs known to be capable of circumventing BD+ protection are DumpHD (versions 0.6 and above, along with some supporting software),[220] MakeMKV,[221] and two applications from DVDFab (Passkey and HD Decrypter).[222]

BD-ROM Mark[edit]

Main article: BD-ROM Mark

ROM Mark is a small amount of cryptographic data that is stored separately from normal Blu-ray Disc data, aiming to prevent replication of the discs. The cryptographic data is needed to decrypt the copyrighted disc content protected by AACS.[223] A specially licensed piece of hardware is required to insert the ROM Mark into the iPhone Backup Extractor Patch Archives during mastering. During replication, this ROM Mark is transferred together with the recorded data to the disc. In consequence, any copies of a disc made with a regular recorder will lack the ROM Mark data and will be unreadable on standard players.[citation needed]

Backward compatibility[edit]

The Blu-ray Disc Association recommends but does not require that Blu-ray Disc drives be capable of reading standard DVDs and CDs, for backward compatibility.[224] Most Blu-ray Disc players are capable of reading both CDs and DVDs; however, a few of the early Blu-ray Disc players released in 2006, such as the Sony BDP-S1, could play DVDs but not CDs.[225][226][227] In addition, with the exception of some early models from LG and Samsung, Blu-ray players cannot play HD DVDs, and HD DVD players cannot play Blu-ray Discs. Some Blu-ray players can also play Video CDs, Super Audio CDs, and/or DVD-Audio discs. All Ultra HD Blu-ray players can play regular Blu-ray Discs, and most can play DVDs and CDs. The PlayStation 4 and PlayStation 5 do not support CDs.[228]

Variations[edit]

High Fidelity Pure Audio (BD-A)[edit]

Main article: High Fidelity Pure Audio Blu-ray

High Fidelity Pure Audio (HFPA) is a marketing initiative, spearheaded by the Universal Music Group, for audio-only Blu-ray optical discs. Launched in 2013 as a potential successor to the compact disc, it has been compared with DVD-A and SACD, which had similar aims.[citation needed]

AVCHD[edit]

Main article: AVCHD

A PanasonicBlu-ray player DMP-BD60 (late 2009) compatible with AVCHD

AVCHD was originally developed as a high-definition format for consumer tapelesscamcorders. Derived from the Blu-ray Disc specification, AVCHD shares a similar random access directory structure but is restricted to lower audio and video bitrates, simpler interactivity, and the use of AVC-video and Dolby AC-3 (or linear PCM) audio. Being primarily an acquisition format, AVCHD playback is not universally recognized among devices that play Blu-ray Discs, 1 Form Proposal - Invoice 1.5 crack serial keygen. Nevertheless, many such devices are capable of playing AVCHD recordings from removable media, such as DVDs, SD/SDHC memory cards, "Memory Stick" cards, and hard disk drives.[229]

AVCREC[edit]

Main article: AVCREC

AVCREC uses a BDAV container to record high-definition content on conventional DVDs.[230] Presently AVCREC is tightly integrated with the Japanese ISDB broadcast standard and is not marketed outside of Japan. AVCREC is used primarily in set-top digital video recorders and in this regard it is comparable to HD REC.[citation needed]

Blu-ray 3D[edit]

The Blu-ray Disc Association (BDA) created a task force made up of executives from the film industry and the consumer electronics and IT sectors to help define standards for putting 3D film and 3D television content on a Blu-ray Disc.[231] On December 17, 2009, the BDA officially announced 3D specs for Blu-ray Disc, allowing backward compatibility with current 2D Blu-ray players,[232] though compatibility is limited by the fact that the longer 3D discs are triple-layer, which normal (2D only) players cannot read. The BDA has said, "The Blu-ray 3D specification calls for encoding 3D video using the "Stereo High" profile defined by Multiview Video Coding (MVC), an extension to the ITU-T H.264 Advanced Video Coding (AVC) codec currently implemented by all Blu-ray Disc players. MPEG4-MVC compresses both left and right eye views with a typical 50% overhead compared to equivalent 2D content, 1 Form Proposal - Invoice 1.5 crack serial keygen, and can provide full 1080p resolution backward compatibility with current 2D Blu-ray Disc players."[233] This means the MVC (3D) stream is backward compatible with H.264/AVC (2D) stream, allowing older 2D devices and software to decode stereoscopic video streams, ignoring additional information for the second view. However, some 3D discs have a user limitation set preventing the disc from being viewed in 2D (though a 2D disc is often included in the packaging).[citation needed]

Sony added Blu-ray 3D support to its PlayStation 3 console via a firmware upgrade on 21 September 2010.[234] The console had previously gained 3D gaming capability via an update on 21 April 2010.[235] Since the version 3.70 software update on August 9, 2011, the PlayStation 3 can play DTS-HD Master Audio and DTS-HD High Resolution Audio while playing 3D Blu-ray.[236]Dolby TrueHD is used on a small minority of Blu-ray 3D releases, and bitstreaming implemented in slim PlayStation 3 models only (original "fat" PS3 models decode internally and send audio as LPCM).[237] The PlayStation VR can also be used to watch these movies in 3D on a PlayStation 4.[238] As of 2018, most major home entertainment studios, such as Walt Disney Studios, Sony Pictures, MGM, and Universal Pictures had discontinued the Blu-ray 3D format in North America, but continued to produce and sell them in other regions such as South America, Europe, Asia, and Australia. Paramount Pictures has ceased sales and productions of 3D Blu-ray discs all over the world, its last 3D releases being Ghost in the Shell and Transformers: The Last Knight, while Warner Bros. still continues to sell and produce 3D Blu-ray discs to this day in all regions, notable titles including: Wonder Woman, Blade Runner 2049, Justice League, Tomb Raider, Rampage, Aquaman, The Lego Movie 2: The Second Part, Shazam!, and Godzilla: King of the Monsters.[citation needed]

Ultra HD Blu-ray[edit]

Main article: Ultra HD Blu-ray

Ultra HD Blu-ray discs are incompatible with existing standard Blu-ray players. They support 4KUHD (3840 × 2160 pixel resolution) video at frame rates up to 60 progressive frames per second,[239] encoded using High-Efficiency Video Coding.[239] The discs support both high dynamic range by increasing the color depth to 10-bit per color and a greater color gamut than supported by conventional Blu-ray video by using the Rec. 2020color space.

See also[edit]

Notes[edit]

  1. ^This is the same as previous optical media formats compact disc and DVD. Exact composition is different as stated in the body of the article.

References[edit]

  1. ^"White Paper Blu-ray Disc Format"(PDF). Blu-ray Disc Association. December 2012. Archived(PDF) from the original on March 13, 2013. Retrieved February 21, 2016.
  2. ^"Data"(PDF). sutlib2.sut.ac.th. Archived(PDF) from the original on February 22, 1 Form Proposal - Invoice 1.5 crack serial keygen. Retrieved February 17, 2014.
  3. ^Blu-ray FAQArchived October 4, 2006, at the Wayback Machine. Blu-ray.com. Retrieved on December 22, 2010.
  4. ^"Blu-ray FAQ". Blu-ray.com. Archived from the original on February 14, 2014. Retrieved February 17, 2014.
  5. ^"6JSC/ALA/16/LC response"(PDF). rda-jsc.org. September 13, 2012. Archived(PDF) from the original on October 14, 2012. Retrieved January 29, 2014.
  6. ^Butler, Harry (February 23, 2011). "Pioneer BDXL BDR-206MBK Review". bit-tech.net. Archived from the original on April 6, 2014. Retrieved February 17, 2014.
  7. ^"DVD Frequently Asked Questions (and Answers)". Jim Taylor. June 27, 2013. Archived from the original on August 22, 2009.
  8. ^"Toshiba Announces Discontinuation of HD DVD Businesses" (Press release). Toshiba. February 19, 2008. Archived from the original on February 25, 2008. Retrieved February 26, 2008.
  9. ^Yomiuri Shimbun. Page 1. July 19, 2009. Ver. 13S.
  10. ^ abc"Blu-ray Discs reach 1.5 million sold, HDM still trails DVD's first two years". Engadget. AOL Inc. February 16, 2008. Archived from the original on February 5, 2015. Retrieved July 29, 2014.
  11. ^"Sony Buys a Facebook Spinoff to Give New Life to Blu-ray". Wired. May 27, 2015. Archived from the original on March 6, 2017. Retrieved March 5, 2017.
  12. ^Morris, Chris (January 8, 2016). "Blu-ray Struggles in the Streaming Age". Fortune. Archived from the original on January 9, 2017. Retrieved October 3, 2018.
  13. ^"Sony Unveils Prototype 20GB Rewritable Optical Disk". Nikkei Business Daily. October 29, 1998. Archived from the original on November 13, 1999. Retrieved October 30, 2019.
  14. ^ abc"White paper Blu-ray Disc Format"(PDF). Blu-ray Disc Founders. August 2004. Retrieved August 11, 2020.
  15. ^"Panasonic, Sony, Philips and TDK Awarded Emmy For Blu-ray Contribution"Archived November 16, 2011, at the Wayback Machine
  16. ^"Sony Develops Next Generation Optical Disk Storage System For the Data Server Market". Sony. November 1, 2000. Archived from the original on July 2, 2011. Retrieved June 15, 2011.
  17. ^Williams, Martyn (October 5, 2000). "New High-Capacity DVD to Hold 22.5GB". PCWorld. Archived from the original on June 1, 2010. Retrieved June 15, 2011.
  18. ^"Sony Shows 'DVR-Blue' Prototype". CD R Info. October 11, 2000. Archived from the original on September 26, 2007. Retrieved October 17, 2007.
  19. ^"Blue Disc B — 1 Form Proposal - Invoice 1.5 crack serial keygen by Blu-ray Disc Association Universal City, CA — Serial Number: 76207670". Trademarkia. Archived from the original on July 17, 2011. Retrieved September 19, 2010.
  20. ^Fox, Barry (February 19, 2002). "Replacement for DVD unveiled". New Scientist. Archived from the original on August 15, 2007. Retrieved October 17, 2007.
  21. ^"Disclosure of Specifications for Large Capacity Optical Disc Recording Format Utilizing Blue-Violet Laser "Blu-ray Disc" Begins". Sony. May 20, 2002. Archived from the original on June 3, 2009. Retrieved March 16, 2009.
Источник: [https://torrent-igruha.org/3551-portal.html]

An Overview of Cryptography

1. INTRODUCTION

Does increased security provide comfort to paranoid people? Or does security provide some very basic protections that we are naive to believe that we don't need? During this time when 1 Form Proposal - Invoice 1.5 crack serial keygen Internet provides essential communication between literally billions of people and is used as a tool for commerce, social interaction, and the exchange of an increasing amount of personal information, AOMEI Backupper Professional crack serial keygen has become a tremendously important issue for every user to deal with.

There are many aspects to security and many applications, ranging from secure commerce and payments to private communications and protecting health care information. One essential aspect for secure communications is that of cryptography. But it is important to note that while cryptography is necessary for secure communications, it is not by itself sufficient. The reader is advised, then, that the topics covered here only describe the first of many steps necessary for better security in any number of situations.

This paper has two major purposes. The first is to define some of the terms and concepts behind basic cryptographic methods, and to offer a way to compare the myriad cryptographic schemes in use today. The second is to provide some real examples of cryptography in use today. (See Section A.4 for some additional commentary on this.)

DISCLAIMER: Several companies, products, and services are mentioned in this tutorial. Such mention is for example purposes only and, unless explicitly stated otherwise, should not be taken as a recommendation or endorsement by the author.

2. BASIC CONCEPTS OF CRYPTOGRAPHY

Cryptography — the science of secret writing — is an ancient art; the first documented use of cryptography in writing dates back to circa 1900 B.C. when an Egyptian scribe used non-standard hieroglyphs in an inscription. Some experts argue that cryptography appeared spontaneously sometime after writing was invented, with applications ranging from diplomatic missives to war-time battle plans. It is no surprise, then, that new forms of cryptography came soon after the widespread development of computer communications. In data and telecommunications, cryptography is necessary when communicating over any untrusted medium, which includes just about any network, particularly the Internet.

There are five primary functions of cryptography:

  1. Privacy/confidentiality: Ensuring that no one can read the message except the intended receiver.
  2. Authentication: The process of proving one's identity.
  3. Integrity: Assuring the receiver that the received message has not been altered in any way from the original.
  4. Non-repudiation: A mechanism to prove that the sender really sent this message.
  5. Key exchange: The method by which crypto keys are shared between sender and receiver.

In cryptography, we start with the unencrypted data, referred to as plaintext. Plaintext is encrypted into ciphertext, which will in turn (usually) be decrypted back into usable plaintext. The encryption and decryption is based upon the type of cryptography scheme being employed and some form of key. For those who like formulas, this process is sometimes written as:

C = Ek(P)
P = Dk(C)

      where P = plaintext, C = ciphertext, E = the encryption method, D = the decryption method, and k = the key.

Given this, there are other functions that might be supported by crypto and other terms that one might hear:

  • Forward Secrecy (aka Perfect Forward Secrecy): This feature protects past encrypted sessions from compromise even if the server holding the messages is compromised. This is accomplished by creating a different key for every session so that compromise of a single key does not threaten the entirely of the communications.
  • Perfect Security: A system that is unbreakable and where the ciphertext conveys no information about the plaintext or the key. To achieve perfect security, the key has to be at least as long as the plaintext, making analysis and even brute-force attacks impossible. One-time pads are an example of such a system.
  • Deniable Authentication (aka Message Repudiation): A method whereby participants in an exchange of messages can be assured in the authenticity of the messages but in such a way that senders can later plausibly deny their participation to a third-party.

In many of the descriptions below, two communicating parties will be referred to as Alice and Bob; this is the common nomenclature in the crypto field and literature to make it easier to identify the communicating parties. If there is a third and fourth party to the communication, they will be referred to as Carol and Dave, respectively. A malicious party is referred to as Mallory, 1 Form Proposal - Invoice 1.5 crack serial keygen, 1 Form Proposal - Invoice 1.5 crack serial keygen eavesdropper as Eve, and a trusted third party as Trent.

Finally, cryptography is most closely associated with the development and creation of the mathematical algorithms used to encrypt and decrypt messages, whereas cryptanalysis is the science of analyzing and breaking encryption schemes. Cryptology is the umbrella term referring to the broad study of secret writing, and encompasses both cryptography and cryptanalysis.

3. TYPES OF CRYPTOGRAPHIC ALGORITHMS

There are several ways of classifying cryptographic algorithms. For purposes of this paper, they will be categorized based on the number of keys that are employed for encryption and decryption, and further defined by their application and use. The three types of algorithms that will be discussed are (Figure 1):

  • Secret Key Cryptography (SKC): Uses a single key for both encryption and decryption; also called symmetric encryption. Primarily used for privacy and confidentiality.
  • Public Key Cryptography (PKC): 1 Form Proposal - Invoice 1.5 crack serial keygen one key for encryption and another for decryption; also called asymmetric encryption. Primarily used for authentication, non-repudiation, and key exchange.
  • Hash Functions: Uses a mathematical transformation to irreversibly "encrypt" information, providing a digital fingerprint. Primarily used for message integrity.

FIGURE 1: Three types of cryptography: secret key, public key, and hash function.

3.1. Secret Key Cryptography

Secret key cryptography methods employ a single key for both encryption and decryption. As shown in Figure 1A, the sender uses the key to encrypt the plaintext and sends the ciphertext to the receiver. The receiver applies the same key to decrypt the message and recover the plaintext. Because a single key is used for both functions, secret key cryptography is also called symmetric encryption.

With this form of cryptography, it is obvious that the key must be known to both the sender and the receiver; that, in fact, is the secret. The biggest difficulty with this approach, of course, is the distribution of the key (more on that later in the discussion of public key cryptography).

Secret key cryptography schemes are generally categorized as being either stream ciphers or block ciphers.

A) Self-synchronizing stream cipher. (From Schneier, 1996, Figure 9.8)

B) Synchronous stream cipher. (From Schneier, 1996, Figure 9.6)

FIGURE 2: Types of stream ciphers.

Stream ciphers operate on a single bit (byte or computer word) at a time and implement some form of feedback mechanism so that the key is constantly changing, 1 Form Proposal - Invoice 1.5 crack serial keygen. Stream ciphers come in several flavors but two are worth mentioning here (Figure 2). Self-synchronizing stream ciphers calculate each bit in the keystream as a function of the previous n bits in the keystream. It is termed "self-synchronizing" because the decryption process can stay synchronized with the encryption process merely by knowing how far into the n-bit keystream it is. One problem is error propagation; a garbled bit in transmission will result in n garbled bits at the receiving side. Synchronous stream ciphers generate the keystream in a fashion independent of the message stream but by using the same keystream generation function at sender and receiver. While stream ciphers do not propagate transmission errors, they are, by their nature, periodic so that the keystream will eventually repeat.

FIGURE 3: Feistel cipher. (Source: Wikimedia Commons)

A block cipher is so-called because the scheme encrypts one fixed-size block of data at a time. In a block cipher, a given plaintext block will always encrypt to the same ciphertext when using the same key (i.e., it is deterministic) whereas the same plaintext will encrypt to different ciphertext in a stream cipher. The most common construct for block encryption algorithms is the Feistel cipher, named for cryptographer Horst Feistel (IBM). As shown in Figure 3, a Feistel cipher combines elements of substitution, permutation (transposition), and key expansion; these features create a large amount of "confusion and diffusion" (per Claude Shannon) in the cipher. One advantage of 1 Form Proposal - Invoice 1.5 crack serial keygen Feistel design is that the 1 Form Proposal - Invoice 1.5 crack serial keygen and decryption stages are similar, sometimes identical, requiring only a reversal of the key operation, thus dramatically reducing the size of the code or circuitry necessary to implement the cipher in software or hardware, respectively. One of Feistel's early papers describing this operation is "Cryptography and Computer Privacy" (Scientific American, May 1973, 228(5), 15-23).

Block ciphers can operate in one of several modes; the following are the most important:

  • Electronic Codebook (ECB) mode is the simplest, most obvious application: the secret key is used to encrypt the plaintext block to form a ciphertext block. Two identical plaintext blocks, then, will always generate the same ciphertext block. ECB is susceptible to a variety of brute-force attacks (because of the fact that the same plaintext block will always encrypt to the same ciphertext), as well as deletion and insertion attacks. In addition, a single bit error in the transmission of the ciphertext results in an error in the entire block of decrypted plaintext.
  • Cipher Block Chaining (CBC) mode adds a feedback mechanism to the encryption scheme; the plaintext is exclusively-ORed (XORed) with the previous ciphertext block prior to encryption so that two identical plaintext blocks will encrypt differently, 1 Form Proposal - Invoice 1.5 crack serial keygen. While CBC protects against many brute-force, deletion, and insertion attacks, a single bit error in the ciphertext yields an entire block error in the decrypted plaintext block and a bit error in the next decrypted plaintext block.
  • Cipher Feedback (CFB) mode is a block cipher implementation as a self-synchronizing stream cipher. CFB mode allows data to be encrypted in units smaller than the block size, which might be useful in some applications such as encrypting interactive terminal input. If we were using one-byte CFB mode, for example, each incoming character is placed into a shift register the same size as the block, encrypted, and the block transmitted. At the receiving side, the ciphertext is decrypted and the extra bits in the block (i.e., everything above and beyond the one byte) are discarded. CFB mode generates a keystream based upon the previous ciphertext (the initial key comes from an Initialization Vector [IV]). In this mode, a single bit error in the ciphertext affects both this block and the following one.
  • Output Feedback (OFB) mode is a block cipher implementation conceptually similar to a synchronous stream cipher. OFB prevents the same plaintext block from generating the same ciphertext block by using an internal feedback mechanism that generates the keystream independently of both the plaintext and ciphertext bitstreams. In OFB, a single bit error in ciphertext yields a single bit error in the decrypted plaintext.
  • Counter (CTR) mode is a relatively modern addition to block ciphers. Like CFB and OFB, CTR mode operates on the blocks as in a stream cipher; like ECB, CTR mode operates on the blocks independently. Unlike ECB, however, Microsoft Toolkit 2.6.7 Latest Free Download 2020 uses different key inputs to different blocks so that two identical blocks of plaintext will not result in the same ciphertext. Finally, each block of ciphertext has specific location within the encrypted message. CTR mode, then, allows blocks to be processed in parallel — thus offering performance advantages when parallel processing and multiple processors are available — but is not susceptible to ECB's brute-force, deletion, and insertion attacks.

A good overview of these different modes can be found at CRYPTO-IT.

Secret key cryptography algorithms in use today — or, at least, important today even if not in use — include:

  • Data Encryption Standard (DES): One of the most well-known and well-studied SKC schemes, DES was designed by IBM in the 1970s and adopted by the National Bureau of Standards (NBS) [now the National Institute of Standards and Technology (NIST)] in 1977 for commercial and unclassified government applications. DES is a Feistel block-cipher employing a 56-bit key that operates on 64-bit blocks. DES has a complex set of rules and transformations that were designed specifically to yield fast hardware implementations and slow software implementations, although this latter point is not significant today since the speed of computer processors is several orders of magnitude faster today than even twenty years ago. DES was based somewhat on an earlier cipher from Feistel called Lucifer which, some sources report, had a 112-bit key. This was rejected, partially in order to fit the algorithm onto a single chip and partially because of the National Security Agency (NSA). The NSA also proposed a number of tweaks to DES that many thought were introduced in order 1 Form Proposal - Invoice 1.5 crack serial keygen weaken the cipher; analysis in the 1990s, however, showed that the NSA suggestions actually strengthened DES, including the removal of a mathematical back door by a change to the design of the S-box (see "The Legacy of DES" by Bruce Schneier [2004]). In April 2021, the NSA declassified a fascinating historical paper titled "NSA Comes Out of the Closet: The Debate over Public Cryptography in the Inman Era" that appeared in Cryptologic Quarterly, Spring 1996.

    DES was defined in American National Standard X3.92 and three Federal Information Processing Standards (FIPS), all withdrawn in 2005:

    • FIPS PUB 46-3: DES (Archived file)
    • FIPS PUB 74: Guidelines for Implementing and Using the NBS Data Encryption Standard
    • FIPS PUB 81: DES Modes of Operation

    Information about vulnerabilities of DES can be obtained from the Electronic Frontier Foundation.

    Two important variants that strengthen DES are:

    • Triple-DES (3DES): A variant of DES that employs up to three 56-bit keys and makes three encryption/decryption passes over the block; 3DES is also described in FIPS PUB 46-3 and was an interim replacement to DES in the late-1990s and early-2000s.

    • DESX: A variant devised by Ron Rivest. By combining 64 additional key bits to the plaintext prior to encryption, effectively increases the keylength to 120 bits.

    More detail about DES, 3DES, and DESX can be found below in Section 5.4.

  • Advanced Encryption Standard (AES): In 1997, NIST initiated a very public, 4-1/2 year process to develop a new secure cryptosystem for U.S. government applications (as opposed to the very closed process in the adoption of DES 25 years earlier). The result, the Advanced Encryption Standard, became the official successor to DES in December 2001. AES uses an SKC scheme called 1 Form Proposal - Invoice 1.5 crack serial keygen Rijndael, a block cipher designed by Belgian cryptographers Joan Daemen and Vincent Rijmen, 1 Form Proposal - Invoice 1.5 crack serial keygen. The algorithm can use a variable block length and key length; the latest specification allowed any combination of keys vyprvpn 4.0.0 crack + new license key apk free download Archives of 128, 192, or 256 bits and blocks of length 128, 192, or 256 bits. NIST initially selected Rijndael in X-Com Ufo Defense 6/8 Page33: crack serial keygen 2000 and formal adoption as the AES standard came 1 Form Proposal - Invoice 1.5 crack serial keygen December 2001. FIPS PUB 197 describes a 128-bit block cipher employing a 128- 192- or 256-bit key. AES is also part of the NESSIE approved suite of protocols. (See also the entries for CRYPTEC and NESSIE Projects in Table 3.)

    The AES process and Rijndael algorithm are described in more detail below in Section 5.9.

  • CAST-128/256: CAST-128 (aka CAST5), described in Request for Comments (RFC) 2144, is a DES-like substitution-permutation crypto algorithm, employing a 128-bit key operating on a 64-bit block. CAST-256 (aka CAST6), described in RFC 2612, is an extension of CAST-128, using a 128-bit block size and a variable length (128, 160, 192, 224, or 256 bit) key. CAST is named for its developers, Carlisle Adams and Stafford Tavares, and is available internationally. CAST-256 was one of the Round 1 algorithms in the AES process.

  • International Data Encryption Algorithm (IDEA): Secret-key cryptosystem written by Xuejia Lai and James Massey, in 1992 and patented by Ascom; a 64-bit SKC block cipher using a 128-bit key.

  • Rivest Ciphers (aka Ron's Code): Named for Ron Rivest, a series of SKC algorithms.

    • RC1: Designed on paper but never implemented.

    • RC2: A 64-bit block cipher using variable-sized keys designed to replace DES. It's code has not been made public although many companies have licensed RC2 for use in their products. Described in RFC 2268.

    • RC3: Found to be breakable during development.

    • RC4: A stream cipher using variable-sized keys; it is widely used in commercial cryptography products. An update to RC4, called Spritz (see also this article), was designed by Rivest and Jacob Schuldt. More detail about RC4 (and a little about Spritz) can be found below in Section 5.13.

    • RC5: A block-cipher supporting a variety of block sizes (32, 64, or 128 bits), key sizes, and number of encryption passes over the data. Described in RFC 2040.

    • RC6: A 128-bit block cipher based upon, and an improvement over, RC5; RC6 was one of the AES Round 2 algorithms.

  • Blowfish: A symmetric 64-bit block cipher invented by Bruce Schneier; optimized for 32-bit processors with large data caches, it is significantly faster than DES on a Pentium/PowerPC-class machine. Key lengths can vary from 32 to 448 bits in length. Blowfish, available freely and intended as a substitute for DES or IDEA, is in use in a large number of products.

  • Twofish: A 128-bit block cipher using 128- 192- or 256-bit keys. Designed to be highly secure and highly flexible, well-suited for large microprocessors, 8-bit smart card microprocessors, and dedicated hardware. Designed by a team led by Bruce Schneier and was one of the Round 2 algorithms in the AES process.

  • Threefish: A large block cipher, supporting 256- 512- and 1024-bit blocks when minecraft premium account generator a key size that matches the block size; by design, the block/key size can grow in increments of 128 bits. Threefish only uses XOR operations, 1 Form Proposal - Invoice 1.5 crack serial keygen, addition, and rotations of 64-bit words; the design philosophy is that an algorithm employing many computationally simple rounds is more secure than one employing highly complex — albeit fewer — rounds. The specification for Threefish is part of the Skein Hash Function Family documentation.

  • Anubis: Anubis is a block cipher, co-designed by Vincent Rijmen who was one of the designers of Rijndael. Anubis is a block cipher, performing substitution-permutation operations on 128-bit blocks and employing keys of length 128 to 3200 bits (in 32-bit increments). Anubis works very much like Rijndael. Although submitted to the NESSIE project, it did not make the final cut for inclusion.

  • ARIA: A 128-bit block cipher employing 128- 192- and 256-bit keys to encrypt 128-bit blocks in 12, 14, and 16 rounds, depending on the key size. Developed by large group of researchers from academic institutions, research institutes, and federal agencies in South Korea in 2003, and subsequently named a national standard. Described in RFC 5794.

  • Camellia: A secret-key, block-cipher crypto algorithm developed jointly by Nippon Telegraph and Telephone (NTT) Corp. and Mitsubishi Electric Corporation (MEC) in 2000. Camellia has some characteristics in common with AES: a 128-bit block size, support for 128- 192- and 256-bit key lengths, and suitability for both software and hardware implementations on common 32-bit processors as well as 8-bit processors (e.g., 1 Form Proposal - Invoice 1.5 crack serial keygen, smart cards, cryptographic hardware, and embedded systems). Also described in RFC 3713. Camellia's application in IPsec is described in RFC 4312 and application in OpenPGP in RFC 5581. Camellia is part of the NESSIE suite of protocols.

  • CLEFIA: Described in RFC 6114, CLEFIA is a 128-bit block cipher employing key lengths of 128, 192, and 256 bits (which is compatible with AES). The CLEFIA Easeus Mobisaver Pro 7.6 Crack With License Code [Win + Mac] was first published in 2007 by Sony Corporation. CLEFIA is one of the new-generation lightweight blockcipher algorithms designed after AES, offering high performance in software and hardware as well as a lightweight implementation in hardware.

  • FFX-A2 and FFX-A10: FFX (Format-preserving, Feistel-based encryption) is a type of Format Preserving Encryption (FPE) scheme that is designed so that the ciphertext has the same format as the plaintext. FPE schemes are used for such purposes as encrypting social security numbers, credit card numbers, limited size protocol traffic, etc.; this means that an encrypted social security number, for example, would still be a nine-digit string. FFX can theoretically encrypt strings of arbitrary length, although it is intended for message sizes smaller than that of AES-128 (2128 points). The FFX version 1.1 specification describes FFX-A2 and FFX-A10, which are intended for 8-128 bit binary strings or 4-36 digit decimal strings.

  • GSM (Global System for Mobile Communications, originally Groupe Spécial Mobile) encryption: GSM mobile phone systems use several stream ciphers for over-the-air communication privacy. A5/1 was developed in 1987 for use in Europe and the U.S. A5/2, developed in 1989, is a weaker algorithm and intended for use outside of Europe and the U.S, 1 Form Proposal - Invoice 1.5 crack serial keygen. Significant flaws were found in both ciphers after the "secret" specifications were leaked in 1994, however, and A5/2 has been withdrawn from use. The newest version, A5/3, employs the KASUMI block cipher. NOTE: Unfortunately, although A5/1 has been repeatedly "broken" (e.g., see "Secret code protecting cellphone calls set loose" [2009] and "Cellphone snooping now easier and cheaper than ever" [2011]), this encryption scheme remains in widespread use, even in 3G and 4G mobile phone networks. Use of this scheme is reportedly one of the reasons that the National Security Agency (NSA) can easily decode voice and data calls over mobile phone networks.

  • GPRS (General Packet Radio Service) encryption: GSM mobile phone systems use GPRS for data applications, and GPRS uses a number of encryption methods, offering different levels of data protection. GEA/0 offers no encryption at all. GEA/1 and GEA/2 are proprietary stream ciphers, employing a 64-bit key and a 96-bit or 128-bit state, respectively. GEA/1 and GEA/2 are most widely used by network service providers today although both have been reportedly broken. GEA/3 is a 128-bit block cipher employing a 64-bit key that is used by some carriers; GEA/4 is a 128-bit clock cipher with a 128-bit key, but is not yet deployed.

  • KASUMI: A block cipher using a 128-bit key that is part of 1 Form Proposal - Invoice 1.5 crack serial keygen Third-Generation Partnership Project (3gpp), formerly known as the Universal Mobile Telecommunications System (UMTS). KASUMI is the intended confidentiality and integrity algorithm for both message content and signaling data for emerging mobile communications systems.

  • KCipher-2: Described in RFC 7008, KCipher-2 is a stream cipher with a 128-bit key and a 128-bit initialization vector, 1 Form Proposal - Invoice 1.5 crack serial keygen. Using simple arithmetic operations, the algorithms offers fast encryption and decryption by use of efficient implementations. KCipher-2 has been used for industrial applications, especially for mobile health monitoring and diagnostic services in Japan.

  • KHAZAD:KHAZAD is a so-called legacy block cipher, operating on 64-bit blocks à la older block ciphers such as DES and IDEA. KHAZAD uses eight rounds of substitution and permutation, 1 Form Proposal - Invoice 1.5 crack serial keygen a 128-bit key.

  • KLEIN: Designed in 2011, KLEIN is a lightweight, 64-bit block cipher supporting 64- 80- and 96-bit keys. KLEIN is designed for highly resource constrained devices such as wireless sensors and RFID tags.

  • Light Encryption Device (LED): Designed in 2011, LED is a lightweight, 64-bit block cipher supporting 64- and 128-bit keys. LED is designed for RFID tags, sensor networks, and other applications with devices constrained by memory or compute power.

  • MARS:MARS is a block cipher developed by IBM and was one of the five finalists in the AES development process, 1 Form Proposal - Invoice 1.5 crack serial keygen. MARS employs 128-bit blocks and a variable key length from 128 to 448 bits. The MARS document stresses the ability of the algorithm's design for high speed, high security, and the ability to efficiently and effectively implement the scheme on a wide range of computing devices.

  • MISTY1: Developed at Mitsubishi Electric Corp., a block cipher using a 128-bit key and 64-bit blocks, and a variable number of rounds. Designed for hardware and software implementations, and is resistant to differential and linear cryptanalysis. Described in RFC 2994, MISTY1 is part of the NESSIE suite.

  • Salsa and 1 Form Proposal - Invoice 1.5 crack serial keygen Salsa20 is a stream cipher proposed for the eSTREAM project by Daniel Bernstein. Salsa20 uses a pseudorandom function based on 32-bit (whole word) addition, bitwise addition (XOR), and rotation operations, aka add-rotate-xor (ARX) operations. Salsa20 uses 1 Form Proposal - Invoice 1.5 crack serial keygen 256-bit key although a 128-bit key variant also exists. In 2008, Bernstein published ChaCha, a new family of ciphers related to Salsa20. ChaCha20, originally defined in RFC 7539 (now obsoleted), is employed (with the Poly1305 authenticator) in Internet Engineering Task Force (IETF) protocols, most notably for IPsec and Internet Key Exchange (IKE), per RFC 7634, and Transaction Layer Security (TLS), per RFC 7905. In 2014, Google adopted ChaCha20/Poly1305 for use in OpenSSL, and they are also a part of OpenSSH. RFC 8439 replaces RFC 7539, and provides an implementation guide for both the ChaCha20 cipher and Poly1305 message authentication code, as well as the combined CHACHA20-POLY1305 Authenticated-Encryption with Associated-Data (AEAD) algorithm.

  • Secure and Fast Encryption Routine (SAFER): A series of block ciphers designed by James Massey for implementation in software and employing a 64-bit block. SAFER K-64, published in 1993, used a 64-bit key and SAFER K-128, published in 1994, employed a 128-bit key. After weaknesses were found, new versions were released called SAFER SK-40, SK-64, and SK-128, using 40- 64- and 128-bit keys, respectively. SAFER+ (1998) used a 128-bit block and was an unsuccessful candidate for the AES project; SAFER++ (2000) was submitted to the NESSIE project.

  • SEED: A block cipher using 128-bit blocks and 128-bit keys. Developed by the Korea Information Security Agency (KISA) and adopted as a national standard encryption algorithm in South Korea. Also described in RFC 4269.

  • Serpent:Serpent is another of the AES finalist algorithms. Serpent supports 128- 192- or 256-bit keys and a block size of 128 bits, and is a 32-round substitution–permutation network operating on a block of four 32-bit words. The Serpent developers opted for a high security margin in the design of the algorithm; they determined that 16 rounds would be sufficient against known attacks but require 32 rounds in an attempt to future-proof the algorithm.

  • SHACAL: SHACAL is a pair of block ciphers based upon the Secure Hash Algorithm (SHA) and the fact that SHA is, at heart, a compression algorithm. As a hash function, SHA repeatedly calls on a compression scheme to alter the state of the data blocks. While SHA (like other hash functions) is irreversible, the compression function can be used for encryption by maintaining appropriate state information. SHACAL-1 is based upon SHA-1 and uses a 160-bit block size while SHACAL-2 is based upon SHA-256 and employs a 256-bit block size; both support key sizes from 128 to 512 bits. SHACAL-2 is one of the NESSIE block ciphers.

  • Simon and Speck: Download flexistarter pro 12 Crack Archives and Speck are a pair of lightweight block ciphers proposed by the NSA in 2013, designed for highly constrained software or hardware environments. (E.g., per the specification, AES requires 2400 gate equivalents and these ciphers require less than 2000.) While both cipher families perform well in both hardware and software, Simon has been optimized for high performance on hardware devices and Speck for performance in software. Both are Feistel ciphers and support ten combinations of block and key size:

  • Skipjack: SKC scheme proposed, along with the Clipper chip, as part of the never-implemented Capstone project. Although the details of the algorithm were never made public, Skipjack was a block cipher using an 80-bit key and 32 iteration cycles per 64-bit block. Capstone, proposed by NIST and the NSA as a standard for public and government use, met with great resistance by the crypto community largely because the design of Skipjack was classified (coupled with the key escrow requirement of the Clipper chip).

  • SM4: Formerly called SMS4, SM4 is a 128-bit block cipher using 128-bit keys and 32 rounds to process a block. Declassified in 2006, SM4 is used in the Chinese National Standard for Wireless Local Area Network (LAN) Authentication and Privacy Infrastructure (WAPI). SM4 had been a proposed cipher for the Institute of Electrical and Electronics Engineers (IEEE) 802.11i standard on security mechanisms for wireless LANs, but has yet to be accepted by the IEEE or International Organization for Standardization (ISO). SM4 is described in SMS4 Encryption Algorithm for Wireless Networks (translated by Whitfield Diffie and George Ledin, 2008) and at the SM4 (cipher) page. SM4 is issued by the Chinese State Cryptographic Authority as GM/T 0002-2012: SM4 (2012).

  • Tiny Encryption Algorithm (TEA): A family of block ciphers developed by Roger Needham and David Wheeler. TEA was originally developed in 1994, and employed a 128-bit key, 64-bit block, and 64 rounds of operation. To correct certain weaknesses in TEA, eXtended TEA (XTEA), aka Block TEA, was released in 1997. To correct weaknesses in XTEA and add versatility, Corrected Block TEA (XXTEA) was published in 1998. XXTEA also uses a 128-bit key, but block size can be any multiple of 32-bit words (with a minimum block size of 64 bits, or two words) and the number of rounds is a function of the block size (~52+6*words), as shown in Table 1.

  • Block Size
    2n
    Key Size
    mn
    Word Size
    n
    Key Words
    m
    Rounds
    T
    326416432
    4872
    96
    243
    4
    36
    36
    6496
    128
    323
    4
    42
    44
    9696
    144
    482
    3
    52
    54
    128128
    192
    256
    642
    3
    4
    68
    69
    72
  • TWINE: Designed by engineers at NEC in 2011, TWINE is a lightweight, 64-bit block cipher supporting 80- and 128-bit keys. TWINE's design goals included maintaining a small footprint in a hardware implementation (i.e., fewer than 2,000 gate equivalents) and small memory consumption in a software implementation.

Although not an SKC scheme, check out Section 5.17 about Shamir's Secret Sharing (SSS).

There are several other references that describe interesting algorithms and even SKC codes dating back decades. Two that leap to mind are the Crypto Museum's Crypto List and John J.G. Savard's (albeit old) A Cryptographic Compendium page.

3.2. Public Key Cryptography

Public key cryptography has been said to be the most significant new development in cryptography in the last 300-400 years. Modern PKC was first described publicly by Stanford University professor Martin Hellman and graduate student Whitfield Diffie in 1976. Their paper described a two-key crypto system in which two parties could engage in a secure communication over a non-secure communications channel without having to share a secret key.

PKC depends upon the existence of so-called one-way functions, or mathematical functions that are easy to compute whereas their inverse function is relatively difficult to compute. Let me give you two simple examples:

  1. Multiplication vs. factorization: Suppose you have two prime numbers, 3 and 7, and you need to calculate the product; it should take almost no time to calculate that value, which is 21. Now suppose, instead, that you have a number that is a product of two primes, 21, and you need to determine those prime factors. You will eventually come up with the solution but whereas calculating the product took milliseconds, factoring will take longer. The problem becomes much harder if we start with primes that have, say, 400 digits or so, because the product will have ~800 digits.
  2. Exponentiation vs. logarithms: Suppose you take the number 3 to the 6th power; again, it is relatively easy to calculate 1 Form Proposal - Invoice 1.5 crack serial keygen. But if you start with the number 729 and need to determine the two integers, x and y so that logx 729 = y, it will take longer to find the two values.

While the examples above are trivial, they do represent two of the functional pairs that are used with PKC; namely, the ease of multiplication and exponentiation versus the relative difficulty of factoring and calculating logarithms, 1 Form Proposal - Invoice 1.5 crack serial keygen. The mathematical "trick" in PKC is to find a trap door in the one-way function so that the inverse calculation becomes easy given knowledge of some item of information.

Generic PKC employs two keys that are mathematically related although knowledge of one key does not allow someone to easily determine the other key. One key is used to encrypt the plaintext and the other key is used to decrypt the ciphertext. The important point here is that it does not matter which key is applied first, but that both keys are required for the process to work (Figure 1B). Because a pair of keys are required, this approach is also called asymmetric cryptography.

In PKC, one of the keys is designated the public key and may be advertised as widely as the owner wants. The other key is designated the private key and is never revealed to another party. It is straight-forward to send messages under this scheme. Suppose Alice wants to send Bob a message. Alice encrypts some information using Bob's public key; Bob decrypts the ciphertext using 1 Form Proposal - Invoice 1.5 crack serial keygen private key. This method could be also used to prove who sent a message; Alice, for example, could encrypt some plaintext with her private key; when Bob decrypts using Alice's public key, he knows that Alice sent the message (authentication) and Alice cannot deny having sent the message (non-repudiation).

Public key cryptography algorithms that are in use today for key exchange or digital signatures include:

  • RSA: The first, and still most common, PKC implementation, named for the three MIT mathematicians who developed it — Ronald Rivest, Adi Shamir, and Leonard Adleman. RSA today is used in hundreds of software products and can be used for key exchange, digital signatures, or encryption of small blocks of data. RSA uses a variable size encryption block and a variable size key. The key-pair is derived from a very large number, n, that is the product of two prime numbers chosen according to special rules; these primes may be 100 or more digits in length each, yielding an n with roughly twice as many digits as the prime factors. The public key information includes n and a derivative of one of the factors of n; an attacker cannot determine the prime factors of n (and, therefore, the private key) from this information alone and that is what makes the RSA algorithm so secure. (Some descriptions of PKC erroneously state that RSA's safety is due to the difficulty in factoring large prime numbers. In fact, large prime numbers, like small prime numbers, only have two factors!) The ability for computers to factor large numbers, and therefore attack schemes such as RSA, is rapidly improving and systems today can find the prime factors of numbers with more than 200 digits. Nevertheless, if a large number is created from 1 Form Proposal - Invoice 1.5 crack serial keygen prime factors that are roughly the same size, there is no known factorization algorithm that will solve the problem in a reasonable amount of time; a 2005 test to factor a 200-digit number took 1.5 years and over 50 years of compute time, 1 Form Proposal - Invoice 1.5 crack serial keygen. In 2009, Kleinjung et al. reported that factoring a 768-bit (232-digit) RSA-768 modulus utilizing hundreds of systems took two years and they estimated that a 1024-bit RSA modulus would take about a thousand times as long. Even so, they suggested that 1024-bit RSA be phased out by 2013. (See the Wikipedia article on integer factorization.) Regardless, one presumed protection of RSA is that users can easily increase the key size to always stay ahead of the computer processing curve. As an aside, the patent for RSA expired in September 2000 which does not appear to have affected RSA's popularity one way or the other. A detailed example of RSA is presented below in Section 5.3.

  • Diffie-Hellman: After the RSA algorithm was published, Diffie and Hellman came Planet Zoo ActivationKey.txt crack serial keygen with their own algorithm. ActivePresenter Pro 8.3.0 Crack With Product Key Full Latest Version 2021 is used for secret-key key exchange only, and not for authentication or digital signatures. More detail about Diffie-Hellman can be found below in Section 5.2.

  • Digital Signature Algorithm (DSA): The algorithm specified in Windows 10 Home Product key With Serial KEYS For 32-64 Bits [Latest] Digital Signature Standard (DSS), provides digital signature capability for the authentication of messages. Described in FIPS PUB 186-4.

  • ElGamal: Designed by Taher Elgamal, ElGamal is a PKC system similar to Diffie-Hellman and used for key exchange. ElGamal is used in some later version of Pretty Good Privacy (PGP) as well as GNU Privacy Guard (GPG) and other cryptosystems.

  • Elliptic Curve Cryptography (ECC): A PKC algorithm based upon elliptic curves. ECC can offer levels of security with small keys comparable to RSA and other PKC methods. It was designed for devices with limited compute power and/or memory, 1 Form Proposal - Invoice 1.5 crack serial keygen, such as smartcards and PDAs. More detail about ECC can be found below in Section 5.8. Other references include the Elliptic Curve Cryptography page and the Online ECC Tutorial page, both from Certicom. See also RFC 6090 for a review of fundamental ECC algorithms and The Elliptic Curve Digital Signature Algorithm (ECDSA) for details about the use of ECC for digital signatures.

  • Identity-Based Encryption (IBE): IBE is a novel scheme first proposed by Adi Shamir in 1984. It is a PKC-based key authentication system where the public key can be derived from some unique information based upon the user's identity, allowing two users to exchange encrypted messages without having an a priori relationship. In 2001, Dan Boneh (Stanford) and Matt Franklin (U.C., Davis) developed a practical implementation of IBE based on elliptic curves and a mathematical construct called the Weil Pairing. In that year, Clifford Cocks (GCHQ) also described another IBE solution based on quadratic residues in composite groups, 1 Form Proposal - Invoice 1.5 crack serial keygen. RFC 5091: Identity-Based Cryptography Standard (IBCS) #1 describes an implementation of IBE using Boneh-Franklin (BF) and Boneh-Boyen (BB1) Identity-based Encryption. More detail about Identity-Based Encryption can be found below in Section 5.16.

  • Public Key Cryptography Standards (PKCS): A set of interoperable standards and guidelines for public key cryptography, designed by RSA Data Security Inc. (These documents are no longer easily available; all links in this section are from archive.org.)

  • Cramer-Shoup: A public key cryptosystem proposed by R. Cramer and V. Shoup of IBM in 1998.

  • Key Exchange Algorithm (KEA): A variation on Diffie-Hellman; proposed as the key exchange method for the NIST/NSA Capstone project.

  • LUC: A public key cryptosystem designed by P.J. Smith and based on Lucas sequences. Can be used for encryption and signatures, using integer factoring.

  • McEliece: A public key cryptosystem based on algebraic coding theory.

For additional information on PKC algorithms, see "Public Key Encryption" (Chapter 8) in Handbook of Applied Cryptography, by A. Menezes, P. van Oorschot, and S. Vanstone (CRC Press, 1996).


A digression: Who invented PKC? I tried to be careful in the first paragraph of this section to 1 Form Proposal - Invoice 1.5 crack serial keygen that Diffie and Hellman "first described publicly" a PKC scheme. Although I have categorized PKC as a two-key system, that has been merely for convenience; the real criteria for a PKC scheme is that it allows two parties to exchange a secret even though the communication with the shared secret might be overheard. There seems to be no question that Diffie and Hellman were first to publish; their method is described in the classic paper, "New Directions in Cryptography," published in the November 1976 issue of IEEE Transactions on Information Theory (IT-22(6), 644-654). As shown in Section 5.2, 1 Form Proposal - Invoice 1.5 crack serial keygen, Diffie-Hellman uses the idea that finding logarithms is relatively harder than performing exponentiation. And, indeed, it is the precursor to modern PKC which does employ two keys. Rivest, Shamir, and Adleman described an implementation that extended this idea in their paper, "A Method Rewasd 5.7.1.4225 Features Key: Obtaining Digital Signatures and Public Key Cryptosystems," published in the February 1978 issue of Elcomsoft Phone Password Breaker crack serial keygen Communications of the ACM (CACM), (21(2), 1 Form Proposal - Invoice 1.5 crack serial keygen, 120-126). Their method, of course, is based upon the relative ease of finding the product of two large prime numbers compared to finding the prime factors of a large number.

Diffie and Hellman (and other sources) credit 1 Form Proposal - Invoice 1.5 crack serial keygen Merkle with first describing a public key distribution system that allows 1 Form Proposal - Invoice 1.5 crack serial keygen parties to share a secret, although it was not a two-key system, per se. A Merkle Puzzle works where Alice creates a large number of encrypted keys, sends them all to Bob so that Bob chooses one at random and then lets Alice know which he has selected. An eavesdropper (Eve) will see all of the keys but can't learn which key Bob has selected (because he has encrypted the response with the chosen key). In this case, Eve's effort to break in is the square of the effort of Bob to choose a key. While this difference may be small it is often sufficient. Merkle apparently took a computer science course at UC Berkeley in 1974 and described his method, but had difficulty making people understand it; frustrated, he dropped the course. Meanwhile, he submitted the paper "Secure Communication Over Insecure Channels," which was published in the CACM in April 1978; Rivest et al.'s paper even makes reference to it. Merkle's method certainly wasn't published first, but he is often credited to have had the idea first.

An interesting question, maybe, but who really knows? For some time, it was a quiet secret that a team at the UK's Government Communications Headquarters (GCHQ) had first developed PKC in the early 1970s. Because of the nature of the work, GCHQ kept the original memos classified. In 1997, however, the GCHQ changed their posture when they realized that there was nothing to gain by continued silence. Documents show that a GCHQ mathematician named James Ellis started research into the key distribution problem in 1969 and that by 1975, James Ellis, Clifford Cocks, and Malcolm Williamson had worked out all of the fundamental details of PKC, yet couldn't talk about their work. (They were, of course, barred from challenging the RSA patent!) By 1999, Ellis, Cocks, and Williamson began to get their due credit in a break-through article in WIRED Magazine. And the National Security Agency (NSA) claims to have knowledge of this type of algorithm as early as 1966. For some additional insight on who knew what when, see Steve Bellovin's "The Prehistory of Public Key Cryptography."


3.3. Hash Functions

Hash functions, also called message digests and one-way encryption, are algorithms that, in essence, use no key (Figure 1C). Instead, a fixed-length hash value is computed based upon the plaintext that makes it impossible for either the contents or length of the plaintext to be recovered. Hash algorithms are typically used to provide a digital fingerprint of a file's contents, often used to ensure that the file has not been altered by an intruder or virus. Hash functions are also commonly employed by many operating systems to encrypt passwords. Hash functions, then, provide a mechanism to ensure the integrity of a file.

Hash functions are also designed so that small changes in the input produce significant differences in the hash value, for example:

Hash string 1: The quick brown fox jumps over the lazy dog
Hash string 2: The quick brown fox jumps over the lazy dog.

MD5 [hash string 1] = 37c4b87edffc5d198ff5a185cee7ee09
MD5 [hash string 2] = 0d7006cd055e94cf614587e1d2ae0c8e

SHA1 [hash string 1] = be417768b5c3c5c1d9bcb2e7c119196dd76b5570
SHA1 [hash string 2] = 9c04cd6372077e9b11f70ca111c9807dc7137e4b

RIPEMD160 [hash string 1] = ee061f0400729d0095695da9e2c95168326610ff
RIPEMD160 [hash string 2] = 99b90925a0116c302984211dbe25b5343be9059e


Let me reiterate that hashes are one-way encryption. You cannot take a hash and "decrypt" it to find the original string that created it, despite the many web sites that claim or suggest otherwise, such as CrackStation, Hashes.com, MD5 Online, md5thiscracker, OnlineHashCrack, XXClone Pro Crack With Latest Version Download (2022) RainbowCrack.

Note that these sites search databases and/or use rainbow tables to find a suitable string that produces the hash in question but one can't definitively guarantee what string originally produced the hash. This is an important distinction. Suppose that you want to crack someone's password, where the hash of the password is stored on the server. Indeed, all you then need is a string that produces the correct hash and you're in! However, you cannot prove that you have discovered the user's password, only a "duplicate key."


Hash algorithms in common use today include:

  • Message Digest (MD) algorithms: A series of byte-oriented algorithms that produce a 128-bit hash value from an arbitrary-length message.

    • MD2 (RFC 1319): Designed for systems with limited memory, such as smart cards. (MD2 has been relegated to historical status, per RFC 6149.)

    • MD4 (RFC 1320): Developed by Rivest, similar to MD2 but designed specifically for fast processing in software. (MD4 has been relegated to historical status, per RFC 6150.)

    • MD5 (RFC 1321): Also developed by Rivest after potential weaknesses were reported in MD4; this scheme is similar to MD4 but is slower because more manipulation is made to the original data. MD5 has been implemented in a large number of products although several weaknesses in the algorithm were demonstrated by German cryptographer Hans Dobbertin in 1996 ("Cryptanalysis of MD5 Compress"). (Updated security considerations for MD5 can be found in RFC 6151.)

  • Secure Hash Algorithm (SHA): Algorithm for NIST's Secure Hash Standard (SHS), described in FIPS PUB 180-4 The status of NIST hash algorithms can be found on their "Policy on Hash Functions" page.

    • SHA-1 produces a 160-bit hash value and was originally published as FIPS PUB 180-1 and RFC 3174. SHA-1 was deprecated by NIST as of the end of 2013 although it is still widely used.

    • SHA-2, originally described in FIPS PUB 180-2 and eventually replaced by FIPS PUB 180-3 (and FIPS PUB 180-4), 1 Form Proposal - Invoice 1.5 crack serial keygen, comprises five algorithms in 1 Form Proposal - Invoice 1.5 crack serial keygen SHS: SHA-1 plus SHA-224, SHA-256, SHA-384, and SHA-512 which can produce hash values that are 224, 256, 384, or 512 bits in length, respectively. SHA-2 recommends use of SHA-1, SHA-224, and SHA-256 for messages less than 264 bits in length, and employs a 512 bit block size; SHA-384 and SHA-512 are recommended for messages less than 2128 bits in length, and employs a 1,024 bit block size. FIPS PUB 180-4 also introduces the concept of a truncated hash in 1 Form Proposal - Invoice 1.5 crack serial keygen, a generic name referring to a hash value based upon the SHA-512 algorithm that has been truncated to t bits; SHA-512/224 and SHA-512/256 are specifically described. SHA-224, -256, -384, and -512 are also described in RFC 4634.

    • SHA-3 is the current SHS algorithm. Although there had not been any successful attacks on SHA-2, NIST decided that having an alternative to SHA-2 using a different algorithm would be prudent. In 2007, they launched a SHA-3 Competition to find that alternative; a list of submissions can be found at The SHA-3 Zoo. In 2012, NIST announced that after reviewing 64 submissions, the winner was Keccak (pronounced "catch-ack"), a family of hash algorithms based on sponge functions. The NIST version can support hash output sizes of 256 and 512 bits.

  • RIPEMD: A series of message digests that initially came from the RIPE (RACE Integrity Primitives Evaluation) project. RIPEMD-160 was designed by Hans Dobbertin, Antoon Bosselaers, and Bart Preneel, and optimized for 32-bit processors to replace the then-current 128-bit hash functions. Other versions include RIPEMD-256, RIPEMD-320, and RIPEMD-128.

  • eD2k: Named for the EDonkey2000 Network (eD2K), the eD2k hash is a root hash of an MD4 hash list of a given file. A root hash is used on peer-to-peer file transfer networks, where a file is broken into chunks; each chunk has its own MD4 hash associated with it and the server maintains a file that contains the hash list WINDOWS 10 PRO x64 40 seriales OKAY all of the chunks. The root hash is the hash of the hash list file.

  • HAVAL (HAsh of VAriable Length): Designed by Y. Zheng, J. Pieprzyk and J. Seberry, a hash algorithm with many levels of security. HAVAL can create hash values that are 128, 160, 192, 224, or 256 bits in length. More details can be found in "HAVAL - A one-way hashing algorithm with variable length output" by Zheng, Pieprzyk, and Seberry (AUSCRYPT '92).

  • The Skein Hash Function Family: The Skein Hash Function Family was proposed to NIST in their 2010 hash function competition. Skein is fast due to using just a few simple computational primitives, secure, and very flexible — per the specification, it can be used as a straight-forward hash, MAC, HMAC, digital signature hash, key derivation mechanism, stream cipher, or pseuo-random number generator. Skein supports internal state sizes of 256, 512 and 1024 bits, and arbitrary output lengths.

  • SM3: SM3 is a 256-bit hash function operating on 512-bit input blocks. Part of a Chinese National Standard, SM3 is issued by the Chinese State Cryptographic Authority as GM/T 0004-2012: SM3 cryptographic hash algorithm (2012) and GB/T 32905-2016: Information security techniques—SM3 cryptographic hash algorithm (2016). More information can also be found at the SM3 (hash function) page.

  • Tiger: Designed by Ross Anderson and Eli Biham, Tiger is designed to be secure, run efficiently on 64-bit processors, and easily replace MD4, MD5, SHA and SHA-1 in other applications. Tiger/192 produces a 192-bit output and is compatible with 64-bit architectures; Tiger/128 and Tiger/160 produce a hash of length 128 and 160 bits, respectively, to provide compatibility with the other hash functions mentioned above.

  • Whirlpool: Designed by V. Rijmen (co-inventor of Rijndael) and P.S.L.M. Barreto, Whirlpool is one of two hash functions endorsed by the NESSIE competition (the other being SHA). Whirlpool operates on messages less than 2256 bits in length and produces a message digest of 512 bits. The design of this hash function is very different than that of MD5 and SHA-1, making it immune to the types of attacks that succeeded on those hashes.

Readers might be interested in HashCalc, a Windows-based program that calculates hash values using a dozen algorithms, including MD5, SHA-1 and several variants, RIPEMD-160, and Tiger. Command line utilities that calculate hash values include sha_verify by Dan Mares (Windows; supports MD5, SHA-1, SHA-2) and md5deep (cross-platform; supports MD5, SHA-1, SHA-256, Tiger, and Whirlpool).


A digression on hash collisions. Hash functions are sometimes misunderstood and some sources claim that no two files can have the same hash value. This is in theory, if not in fact, incorrect. Consider a hash function that provides a 128-bit hash value. There are, then, 2128 possible hash values. But there are an infinite number of possible files and ∞ >> 2128. Therefore, there have to be multiple files — in fact, there have to be an infinite number of files! — that have the same 128-bit hash value. (Now, while even this is theoretically correct, it is not true in practice because 1 Form Proposal - Invoice 1.5 crack serial keygen algorithms are designed to work with a limited message size, as mentioned above. For example, SHA-1, SHA-224, and SHA-256 produce hash values that are 160, 224, and 256 bits in length, respectively, and limit the message length to less than 264 bits; SHA-384 and all SHA-256 variants limit the message length to less than 2128 bits. Nevertheless, hopefully you get my point — and, alas, even if you don't, do know that there are multiple files that have the same MD5 or SHA-1 hash values.)

The difficulty is not necessarily in finding two files with the same hash, but in finding a second file that has the same hash value as a given first file. Consider this example. A human head has, generally, no more than ~150,000 hairs. Since there are more than 7 billion people on earth, we know that there are a lot of people with the same number of hairs on their head. Finding two people with the same number of hairs, then, would be relatively simple. The harder problem is choosing one person (say, you, the reader) and then finding another person who has the same number of hairs on their head 1 Form Proposal - Invoice 1.5 crack serial keygen you have on yours.

This is somewhat similar to the Birthday Problem. We know from probability that if you choose a random group of ~23 people, the probability is about 50% that two will share a birthday (the probability goes up to 99.9% with a group of 70 people). However, if you randomly select one person in a group of 23 and try to find a match to that person, the probability is only about 6% of finding a match; you'd need a group of 253 for a 50% probability of a shared birthday to one of the people chosen at random (and a group of more than 4,000 to obtain a 99.9% probability).

What is hard to do, then, is to try to create a file that matches a given hash value so as to force a hash value collision — which is the reason that hash functions are used extensively for information security and computer forensics applications. Alas, researchers as far back as 2004 found that practical collision attacks could be launched on MD5, SHA-1, and other hash algorithms and, today, it is generally recognized that MD5 and SHA-1 are pretty much broken. 1 Form Proposal - Invoice 1.5 crack serial keygen interested in this problem should read the following:

  • AccessData. (2006, April). MD5 Collisions: The Effect on Computer Forensics. AccessData White Paper.
  • Burr, W. (2006, March/April). Cryptographic hash standards: Where do we go from here?IEEE Security & Privacy, 4(2), 88-91.
  • Dwyer, D. (2009, June 3). SHA-1 Collision Attacks Now 252. SecureWorks Research blog.
  • Gutman, P., Naccache, D., & Palmer, C.C. (2005, May/June). When hashes collide. IEEE Security & Privacy, 3(3), 68-71.
  • Kessler, G.C. (2016). The Impact of MD5 File Hash Collisions on Digital Forensic Imaging. Journal of Digital Forensics, Security & Law, 11(4), 129-138.
  • Kessler, G.C. (2016). The Impact of SHA-1 File Hash Collisions on Digital Forensic Imaging: A Follow-Up Experiment. Journal of Digital Forensics, Security & Law, 11(4), 139-148.
  • Klima, V. (2005, March). Finding MD5 Collisions - a Toy For a Notebook.
  • Lee, R. (2009, January 7). Law Is Not A Science: Admissibility of Computer Evidence and MD5 Hashes. SANS Computer Forensics blog.
  • Leurent, G. & Peyrin, T. (2020, January). SHA-1 is a Shambles: First Chosen-Prefix Collision on SHA-1 and Application to the PGP Web of Trust. Real World Crypto 2020.
  • Leurent, G. & Peyrin, T. (2020, January). SHA-1 is a Shambles: First Chosen-Prefix Collision on SHA-1 and Application to the PGP Web of Trust.(paper)
  • Stevens, M., 1 Form Proposal - Invoice 1.5 crack serial keygen, Bursztein, E., Karpman, P., Albertini, A., 1 Form Proposal - Invoice 1.5 crack serial keygen, & Markov, Y. (2017). The first collision for full SHA-1.
  • Stevens, M., Karpman, P., & Peyrin, T. (2015, October 8). Freestart collision on full SHA-1. Cryptology ePrint Archive, Report 2015/967.
  • Thompson, E. (2005, February). MD5 collisions and the impact on computer forensics. Digital Investigation, 2(1), 36-40.
  • Wang, X., Feng, D., Lai, X., & Yu, H. (2004, August). Collisions for Hash Functions MD4, MD5, HAVAL-128 and RIPEMD.
  • Wang, X., Yin, Y.L., & Yu, H. (2005, February 13). Collision Search Attacks on SHA1.

Readers are also referred to the Eindhoven University of Technology HashClash Project Web site. for For additional information on hash functions, see David Hopwood's MessageDigest Algorithms page and Peter Selinger's MD5 Collision Demo page. For historical purposes, take a look at the situation with hash collisions, circa 2005, in RFC 4270.

In October 2015, the SHA-1 Freestart Collision was announced; see a report by Bruce Schneier and the developers of the attack (as well as the paper above by Stevens et al. (2015)). In February 2017, the first SHA-1 collision was announced on the Google Security Blog and Centrum Wiskunde & Informatica's Shattered page. See also the paper by Stevens et al. (2017), listed above. If ths isn't enough, see the SHA-1 is a Shambles Web page and the Leurent & Peyrin paper, listed above.

For an interesting twist on this discussion, read about the Nostradamus attack reported at Predicting the winner of the 2008 US Presidential Elections using a Sony PlayStation 3 (by M. Stevens, A.K. Lenstra, and B. de Weger, November 2007).


Finally, note that certain extensions of hash functions are used for a variety of information security and digital forensics applications, such as:

  • Hash libraries, aka hashsets, are sets of hash values corresponding to known files. A hashset containing the hash values of all files known to be a part of a given operating system, for example, could form a set of known good files, and could be ignored in an investigation for malware or other suspicious file, whereas as hash library of known child pornographic images could form a set of known bad files and be the target of such an investigation.
  • Rolling hashes refer to a set of hash values that are computed based upon a fixed-length "sliding window" through the input. As an example, a hash value might be computed on bytes 1-10 of a file, then on bytes 2-11, 3-12, 4-13, etc.
  • Fuzzy hashes are an area of intense research and represent hash values that represent two inputs that are similar. Fuzzy hashes are used to detect documents, images, or other files that are close to each other with respect to content. See "Fuzzy Hashing" by Jesse Kornblum for a good treatment of this topic.

3.4. Why Three Encryption Techniques?

So, why are there so many different types of cryptographic schemes? Why can't we do everything we need with just one?

The answer is that each scheme is optimized for some specific cryptographic application(s). Hash functions, for example, are well-suited for ensuring data integrity because any change made to the contents of a message will result in the receiver calculating a different hash value than the one placed in the 1 Form Proposal - Invoice 1.5 crack serial keygen by the sender. Since it is highly unlikely that two different messages will yield the same hash value, data integrity is ensured to a high degree of confidence.

Secret key cryptography, on the other hand, is ideally suited to encrypting messages, thus providing privacy and confidentiality. The sender can generate a session key on a per-message basis to encrypt the message; the receiver, of course, needs the same session key in order to decrypt the message.

Key exchange, of course, 1 Form Proposal - Invoice 1.5 crack serial keygen, is a key application of public key cryptography (no pun intended). Asymmetric schemes can also be used for non-repudiation and user authentication; if the receiver can obtain the session key encrypted with the sender's private key, then only this sender could have sent the message. Public key cryptography could, 1 Form Proposal - Invoice 1.5 crack serial keygen, theoretically, also be used to encrypt messages although this is rarely done because secret key cryptography values can generally be computed about 1000 times faster than public key cryptography values.

FIGURE 4: Use of the three cryptographic techniques for secure communication.


Figure 4 puts all of this together and shows how a hybrid cryptographic scheme combines all of these functions to form a secure transmission comprising a digital signature and digital envelope. In this example, the sender of the message is Alice and the receiver is Bob.

A digital envelope comprises an encrypted message and an encrypted session key. Alice uses secret key cryptography to encrypt her message using the session key, which she generates at random with each session. Alice then encrypts the session key using Bob's public key. The encrypted message and encrypted session key together form the digital envelope. Upon receipt, Bob recovers the session secret key using his private key and then decrypts the encrypted message.

The digital signature is formed in two steps. First, Alice computes the hash value of her message; next, she encrypts the hash value with her private key. Upon receipt of the digital signature, Bob recovers the hash value calculated by Alice by decrypting the digital signature with Alice's public key. Bob can then apply the hash function to Alice's IObit Smart Defrag PRO 6.6.0 - September 2020 crack serial keygen message, which he has already decrypted (see previous paragraph). If the resultant hash value is not the same as the value supplied by Alice, then Bob knows that the message has been altered; if the hash values are the same, Bob should believe that the message he received is identical to the one that Alice sent.

This scheme also provides nonrepudiation since it proves that Alice sent the message; if the hash value recovered by Bob using Alice's public key proves that the message has not been altered, then only Alice could have created the digital signature. Bob also has proof that he is the intended receiver; if he can correctly decrypt the message, then he must have correctly decrypted the session key meaning that his is the correct private key.

This diagram purposely suggests a cryptosystem where the session key is used for just a single session. Even if this session key is somehow broken, only this session will be compromised; the session key for 1 Form Proposal - Invoice 1.5 crack serial keygen next session is not based upon the key for this session, just as this session's key was not dependent on the key from the previous session. This is known as Perfect Forward Secrecy; you might lose one session key due to a compromise but you won't lose all of them. (This was an issue in the 2014 OpenSSL vulnerability known as Heartbleed.)

3.5. The Significance of Key Length

In a 1998 article in the industry literature, a writer made the claim that 56-bit keys did not provide as adequate protection for DES at that time as they 1 Form Proposal - Invoice 1.5 crack serial keygen in 1975 because computers were 1000 times faster in 1998 than in 1975. Therefore, the writer went on, we needed 56,000-bit keys in 1998 instead of 56-bit keys to provide adequate protection. The conclusion was then drawn that because 56,000-bit keys are infeasible (true), we should accept the fact that we have to live with weak cryptography (false!). The major error here is that the writer did not take into account that the number of possible key values double whenever a single bit is added to the key length; thus, a 57-bit key has twice as many values as a 56-bit key (because 257 is two times 256). In fact, a 66-bit key would have 1024 times more values than a 56-bit key.

But this does bring up the question — "What is 1 Form Proposal - Invoice 1.5 crack serial keygen significance of key length as it affects the level of protection?"

In cryptography, size does matter. The larger the key, the harder it is to crack a block of encrypted data. The reason that large keys offer more protection is almost obvious; computers have made it easier to attack ciphertext by using brute force methods rather than by attacking the mathematics (which are generally well-known anyway). With a brute force attack, the attacker merely generates every possible key and applies it to the ciphertext. Any resulting plaintext that makes sense offers a candidate for a legitimate key. This was the basis, of course, of the EFF's attack on DES.

Until the mid-1990s or so, brute force attacks were beyond the capabilities of computers that were within the budget of the attacker community. By that time, however, significant compute power was typically available and accessible. General-purpose computers such as PCs were already being used 1 Form Proposal - Invoice 1.5 crack serial keygen brute force attacks. For serious attackers with money to spend, such as some large companies or governments, Field Programmable Gate Array (FPGA) or Application-Specific Integrated Circuits (ASIC) technology offered the ability to build specialized chips that could provide even faster and 1 Form Proposal - Invoice 1.5 crack serial keygen solutions than a PC. As an example, the AT&T Optimized Reconfigurable Cell Array (ORCA) FPGA chip cost about $200 and could test 30 million DES keys per second, while a $10 ASIC chip could test 200 million DES keys per second; compare that to a PC which might be able to test 40,000 keys per second. Distributed attacks, harnessing the power of up to tens of thousands of powerful CPUs, are now commonly employed to try to brute-force crypto keys.

Type of AttackerBudgetToolTime and Cost
Per Key Recovered
Key Length Needed
For Protection
In Late-1995
40 bits56 bits
Pedestrian HackerTinyScavenged
computer
time
1 weekInfeasible45
$400FPGA5 hours
($0.08)
38 years
($5,000)
50
Small Business$10,000FPGA12 minutes
($0.08)
18 months
($5,000)
55
Corporate Department$300KFPGA24 seconds
($0.08)
19 days
($5,000)
60
ASIC0.18 seconds
($0.001)
3 hours
($38)
Big Company$10MFPGA7 seconds
($0.08)
13 hours
($5,000)
70
ASIC0.005 seconds
($0.001)
6 minutes
($38)
Intelligence Agency$300MASIC0.0002 seconds
($0.001)
12 seconds
($38)
75

Table 2 — from a 1996 article discussing both why exporting 40-bit keys was, in essence, no crypto at all and why DES' days were numbered — shows what DES key sizes were needed to protect data from attackers with different time and financial resources. This information was not merely academic; one of the basic tenets of any security system is to have an idea of what you are protecting and from whom are you protecting it! The table clearly shows that a 40-bit key was essentially worthless against even the most unsophisticated attacker. On the other hand, 56-bit keys were fairly strong unless you might be subject to some pretty serious corporate or government espionage. But note that even 56-bit keys were clearly on the decline in their value and that the times in the table were worst cases.

So, how big is big enough? DES, invented in 1975, was still in use at the turn of the century, nearly 25 years later. If we take that to be a design criteria (i.e., a 20-plus year lifetime) and we believe Moore's Law ("computing power doubles every 18 months"), 1 Form Proposal - Invoice 1.5 crack serial keygen, then a key size extension of 14 bits (i.e., a factor of more than 16,000) should be adequate. The 1975 DES proposal suggested 56-bit keys; by 1995, a 70-bit key would have been required to offer equal protection and an 85-bit key necessary by 2015.

A 256- or 512-bit SKC key will probably suffice for some time because that length keeps us ahead of the brute force capabilities of the attackers. Note that while a large key is good, a huge key may not always be better; for example, expanding PKC keys beyond the current 2048- or 4096-bit lengths doesn't add any necessary protection at this time. Weaknesses in cryptosystems are largely based upon key management rather than weak keys.

Much of the discussion above, including the table, is based on the paper "Minimal Key Lengths for Symmetric Ciphers to Provide Adequate Commercial Security" by M. Blaze, W. Diffie, R.L. Rivest, B. Schneier, T. Shimomura, E. Thompson, and M. Wiener (1996).

The most effective large-number factoring methods today use a mathematical Number Field Sieve to find a certain number of relationships and then uses a matrix operation to solve a linear equation to produce the two prime factors. The sieve step actually involves a large number of operations that can be performed in parallel; solving the linear equation, however, requires a supercomputer. Indeed, finding the solution to the RSA-140 challenge in February 1999 — factoring a 140-digit (465-bit) prime number — required 200 computers across the Internet about 4 weeks 1 Form Proposal - Invoice 1.5 crack serial keygen the first step and a Cray computer 100 hours and 810 MB of memory to do the second step.

In early 1999, Shamir (of RSA fame) described a new machine that could increase factorization speed by 2-3 orders of magnitude. Although no detailed plans were provided nor is one known to have been built, the concepts of TWINKLE (The Weizmann Institute Key Locating Engine) could result in a specialized piece of hardware that would cost about $5000 and have the processing power of 100-1000 PCs. There still appear to be many engineering details that have to be worked out before such a machine could be built. Furthermore, the hardware improves the sieve step only; the matrix operation is not optimized at all by this design and the complexity of this step grows rapidly with key length, both in terms of processing time and memory requirements. Nevertheless, this plan conceptually puts 512-bit keys within reach of being factored. Although most PKC schemes allow keys that are 1024 bits and longer, Shamir claims that 512-bit RSA keys "protect 95% of today's E-commerce on the Internet." (See Bruce Schneier's Crypto-Gram Jogos de Construção de Baralhos de Graça para Baixar 15, 1999) for more information.)

It is also interesting to note that while cryptography is good and strong cryptography is better, long keys may disrupt the nature of the randomness of data files. Shamir and van Someren ("Playing hide and seek with stored keys") have noted that a new generation of viruses can be written that will find files encrypted with long keys, making them easier to find by intruders and, therefore, more prone to attack.

Finally, U.S. government policy has tightly controlled the export of crypto products since World War II. Until the mid-1990s, export outside of North America of cryptographic products using keys greater than 40 bits in length was prohibited, which made those products essentially worthless in the marketplace, particularly for electronic commerce; today, crypto products are widely available on the Internet without restriction. The U.S. Department of Commerce Bureau of Industry and Security maintains an Encryption FAQ web page with more information about the current state of encryption registration.


Without meaning to editorialize too much in this tutorial, a bit of historical context might be helpful. In the mid-1990s, the U.S. Department of Commerce still classified cryptography as a munition and limited the export of any products that contained crypto. For that reason, browsers in the 1995 era, such as Internet Explorer and Netscape, had a domestic version with 128-bit encryption (downloadable only in the U.S.) and an export version with 40-bit encryption. Many cryptographers felt Dr. Salmans Windows Power Tools 2.85 crack serial keygen the export limitations should be lifted because they only applied to U.S. products and seemed to have been put into place by policy makers who believed that only the U.S. knew how to build strong crypto algorithms, ignoring the work ongoing in Australia, Canada, Israel, South Africa, the U.K., and other locations in the 1990s. Those restrictions were lifted by 1996 or 1997, but there is still a prevailing attitude, apparently, that U.S. crypto algorithms are the only strong ones around; consider Bruce Schneier's blog in June 2016 titled "CIA Director John Brennan Pretends Foreign Cryptography Doesn't Exist." Cryptography is a decidedly international game today; note the many countries mentioned above as having developed various algorithms, not the least of which is the fact that NIST's Advanced Encryption Standard employs an algorithm submitted by cryptographers from Belgium. For more evidence, see Schneier's Worldwide Encryption Products Survey (February 2016).


On a related topic, public key crypto schemes can be used for several 1 Form Proposal - Invoice 1.5 crack serial keygen, including key exchange, digital signatures, authentication, and more. In those PKC systems used for SKC key exchange, the PKC key lengths are chosen so as to be resistant to some selected level of attack. The length of the secret keys exchanged via that system have to have at least the same level of attack resistance. Thus, the three parameters of such a system — system strength, secret key strength, and public key strength — must be matched. This topic is explored in more detail in Determining Strengths For Public Keys Used For Exchanging Symmetric Keys (RFC 3766).

4. TRUST MODELS

Secure use of cryptography requires trust. While secret key cryptography can ensure message confidentiality and hash codes can ensure integrity, none of this works without trust. In SKC, Alice and Bob had to share a secret key. PKC solved the secret distribution problem, but how does Alice really know that Bob is who he says he is? Just because Bob has a public and private key, and purports to be "Bob," how does Alice know that a malicious person (Mallory) is not pretending to be Bob?

There are a number of trust models employed by various cryptographic schemes. This section will explore three of them:

  • The web of trust employed by Pretty Good Privacy (PGP) users, who hold their own set of trusted public keys.
  • Kerberos, a secret key distribution scheme 1 Form Proposal - Invoice 1.5 crack serial keygen a trusted third party.
  • Certificates, which allow a set of trusted third parties to authenticate each other and, by implication, each other's users.

Each of these trust models differs in complexity, general applicability, scope, and scalability.

4.1. PGP Web of Trust

Pretty Good Privacy (described more below in Section 5.5) is a widely used private e-mail scheme based on public key methods. A PGP user maintains a local keyring of all their known and trusted public keys. The user makes their own determination about the trustworthiness of a key using what is called a "web of trust."

FIGURE 5: GPG keychain.

Figure 5 shows a PGP-formatted keychain from the GNU Privacy Guard (GPG) software, an implementation of the OpenPGP standard. This is a section of my keychain, so only includes public keys from individuals whom I know and, presumably, trust. Note that keys are associated with e-mail addresses rather than individual names.

In general, the PGP Web of trust works as follows. Suppose that Alice needs Bob's public key. Alice could just ask Bob for it directly via e-mail or download the public key from a PGP key server; this server might a well-known PGP key repository or a site that Bob maintains himself. In fact, Bob's public key might be stored or listed in many places. (My public key, for example, can be found at https://www.garykessler.net/pubkey.html or at several public PGP key servers, including https://keys.openpgp.org.) Alice is prepared to believe that Bob's public key, as stored at these locations, is valid.

Suppose Carol claims to hold Bob's public key and offers to give the key to Alice. How does Alice know that Carol's version of Bob's key is valid or if Carol is actually giving Alice a key that will allow Mallory access to messages? The answer is, "It depends." If Alice trusts Carol and Carol says that she thinks that her version of Bob's key is valid, then Alice may — at her option — trust that key. And trust is not necessarily transitive; if Dave has a copy of Bob's key and Carol trusts Dave, it does Yipe! III v1.1 crack serial keygen necessarily follow that Alice trusts Dave even if she does trust Carol.

The point here is that who Alice trusts and how she makes that determination is strictly up to Alice. PGP makes no statement and has no protocol about how one user determines whether they trust another user or not. In any case, encryption and signatures based on public keys can only be used when the appropriate public key is on the user's keyring.

4.2. Kerberos

Kerberos is a commonly used authentication scheme on the Internet. Developed by MIT's Project Athena, Kerberos is named for the three-headed dog who, according to Greek mythology, guards the entrance of Hades (rather than the exit, for some reason!).

Kerberos employs a client/server architecture and provides user-to-server authentication rather than host-to-host authentication. In this model, security and authentication will be based on secret key technology where every host on the network has its own secret key. It would clearly be unmanageable if every host had to know the keys of all other hosts so a secure, trusted host somewhere on the network, known as a Key Distribution Center (KDC), knows the keys for all of the hosts (or at least some of the hosts within a portion of the network, called a realm). In this way, when a new node is brought online, only the KDC and the new node need to be configured with the node's key; keys can be distributed physically or by some other secure means.

FIGURE 6: Kerberos architecture.


The Kerberos Server/KDC has two main functions (Figure 6), known as the Authentication Server (AS) and Ticket-Granting Server (TGS). The steps in establishing an authenticated session between an application client and the application server are:
  1. The Kerberos client software establishes a connection with the Kerberos server's AS function. The AS first 1 Form Proposal - Invoice 1.5 crack serial keygen that the client is who it purports to be. The AS then provides the client with a secret key for this login session (the TGS session key) and a ticket-granting ticket (TGT), which gives the client permission to talk to the TGS. The ticket has a finite lifetime so that the authentication process is repeated periodically.
  2. The client now communicates with the TGS to obtain the Application Server's key so that it (the client) can establish a connection to the service it wants. The client supplies the TGS with the TGS session key and TGT; the TGS responds with an application session key (ASK) and an encrypted form of the Application Server's secret key; this secret key is never sent on the network in any other form.
  3. The client has now authenticated itself and can prove its identity to the Application Server by supplying the Kerberos ticket, application session key, and encrypted Application Server secret key. The Application Server responds with similarly encrypted information to authenticate itself to the client. At this point, the client can initiate the intended service requests (e.g., Telnet, FTP, HTTP, or e-commerce transaction session establishment).

The current version of this protocol is Kerberos V5 (described in RFC 1510). While the details of their operation, functional capabilities, and message formats are different, the conceptual overview above pretty much holds for both. One primary difference is that Kerberos V4 uses only DES to generate keys and encrypt messages, while V5 allows other schemes to be employed (although DES is still the MapleSoft Maple 2021.2 Crack Free Full Version Key Download widely algorithm used).

4.3. Public Key Certificates and Certificate Authorities

Certificates and Certificate Authorities (CA) are necessary for widespread use of cryptography for e-commerce applications. While 1 Form Proposal - Invoice 1.5 crack serial keygen combination of secret and public key cryptography can solve the business issues discussed above, crypto cannot alone address the trust issues that must exist between a customer and vendor in the very fluid, very dynamic e-commerce relationship. How, for example, does one site obtain another party's public key? How does a recipient determine if a public key really belongs to the sender? How does the recipient know that the sender is using their public key for a legitimate purpose for which they are authorized? When does a public key expire? How can a key be revoked in case of compromise or loss?

The basic concept of a certificate is one that is familiar to all of us. A driver's license, credit card, or SCUBA certification, for example, identify us to others, indicate something that we are authorized to do, have an expiration date, and identify the authority that granted the certificate.

As complicated as this may sound, it really isn't. Consider driver's licenses. I have one issued by the State of Florida. The license establishes my identity, indicates the type of vehicles that I can operate and the fact that I must wear corrective lenses while doing so, identifies the issuing authority, and notes that I am an organ donor. When I drive in other states, the other jurisdictions throughout the U.S. recognize the authority of Florida to issue this "certificate" and they trust the information it contains. When I leave the U.S., everything changes. When I am in Aruba, Australia, Canada, Israel, and many other countries, they will accept not the Florida license, per se, but any license issued in the U.S. This analogy represents the certificate trust chain, where even certificates carry certificates.

For purposes of electronic transactions, 1 Form Proposal - Invoice 1.5 crack serial keygen, certificates are digital documents. The specific functions of the certificate include:

  • Establish identity: Associate, or bind, a public key to an individual, organization, corporate position, or other entity.
  • Assign authority: Establish what actions the holder may or may not take based upon this certificate.
  • Secure confidential information (e.g., encrypting the session's symmetric key for data confidentiality).

Typically, a certificate contains a public key, a name, an expiration date, the name of the authority that issued the certificate (and, therefore, is vouching for the identity of the user), a serial number, any pertinent policies describing how the certificate was issued and/or how the certificate may be used, the digital signature of the certificate issuer, and perhaps other information.

FIGURE 7: VeriSign Class 3 certificate.

A sample abbreviated certificate is shown in Figure 7. This is a typical certificate found in a browser, in this case, Mozilla Firefox (MacOS). While this is a certificate issued by VeriSign, many root-level certificates can be found shipped with browsers. When the browser makes a connection to a secure Web site, the Web server sends its public key certificate to the browser. The browser then checks the certificate's signature 1 Form Proposal - Invoice 1.5 crack serial keygen the public key that it has stored; if there is a match, the certificate is taken as valid and the Web site verified by this certificate is considered to be "trusted."

The most widely accepted certificate format is the one defined in International Telecommunication Union Telecommunication Standardization Sector (ITU-T) Recommendation X.509. Rec. X.509 is a specification used around the world and any applications complying with X.509 can share certificates. Most certificates today comply with X.509 Version 3 and contain the following information:

  • Version number
  • Certificate serial number
  • Signature algorithm identifier
  • Issuer's name and unique identifier
  • Validity (or operational) period
  • Subject's name and unique identifier
  • Subject public key information
  • Standard extensions
    • Certificate appropriate use definition
    • Key usage limitation definition
    • Certificate policy information
  • Other extensions
    • Application-specific
    • CA-specific

Certificate authorities are the repositories for public keys and can be any agency that issues certificates. A company, for example, may issue certificates to its employees, a college/university to its students, a store to its customers, an Internet service provider to its users, or a government to its constituents.

When a sender needs an intended receiver's public key, the sender must get that key from the receiver's CA. That scheme is straight-forward if the sender and receiver have certificates issued by the same CA. If not, how does the sender know to trust the foreign CA? One industry wag has noted, about trust: "You are either born with it or have it granted upon you." Thus, some CAs will be trusted because they are known to be reputable, such as the CAs operated by AT&T Services, Comodo, DigiCert (formerly GTE Cybertrust), EnTrust, Broadcom (formerly Symantec, formerly VeriSign), and Thawte. CAs, in turn, form trust relationships with other CAs. Thus, if a user queries a foreign CA for information, the user may ask to see a list of CAs that establish a "chain of trust" back to the user.

One major feature to look for in a CA is their identification policies and procedures. When a user generates a key pair and forwards the public key to a CA, the CA has to check the sender's identification and takes any steps necessary to assure itself that the request is really coming from the advertised sender. Different CAs have different identification policies and will, therefore, be trusted differently by other CAs. Verification of identity is just one of many issues that are part of a CA's Certification Practice Statement (CPS) and policies; other issues include how the CA protects the public keys in its care, how lost or compromised keys are revoked, and how the CA protects its own private keys.

As a final note, CAs are not immune to attack and certificates themselves are able to be counterfeited. One of the first such episodes occurred at the turn of the century; on January 29 and 30, 2001, two VeriSign Class 3 code-signing digital certificates were issued to an individual who fraudulently claimed to be a Microsoft employee (CERT/CC CA-2001-04 and Microsoft Security Bulletin MS01-017 - Critical). Problems have continued over the years; good write-ups on this can be found at "Another Certification Authority Breached (the 12th!)" and "How Cybercrime Exploits Digital Certificates." Readers are also urged to read "Certification Authorities Under Attack: A Plea for Certificate Legitimation" (Oppliger, R., January/February 2014, IEEE Internet Computing, 18(1), 40-47).

As a partial way to address this issue, the Internet Security Research Group (ISRG) 1 Form Proposal - Invoice 1.5 crack serial keygen the Automated Certificate Management Environment (ACME) protocol. ACME is a communications protocol that streamlines the process of deploying a Public Key Infrastructure (PKI) by automating interactions between CAs and Web servers that wish to obtain a certificate. More information can 1 Form Proposal - Invoice 1.5 crack serial keygen found at the Let's Encrypt Web site, an ACME-based CA service provided by the ISRG.

4.4. Summary

The paragraphs above describe three very different trust models. It is hard to say that any one is better than the others; it depends upon your application. One of the biggest and fastest growing applications of cryptography today, though, is electronic commerce (e-commerce), a term that itself begs for a formal definition.

PGP's web of trust is easy to maintain and very much based on the reality of users as people. The model, however, is limited; just how many public keys can a single user reliably store and maintain? And what if you are using the "wrong" computer when you want to send a message and can't access your keyring? How easy it is to revoke a key if it is compromised? PGP may also not scale well to an e-commerce scenario of secure communication between total strangers on short-notice.

Kerberos overcomes many of the problems of PGP's web of trust, in that it is scalable and its scope can be very large. However, it also requires that the Kerberos server have a priori knowledge of all client systems prior to any transactions, which makes it unfeasible for "hit-and-run" client/server relationships as seen in e-commerce.

Certificates and the collection of CAs will form a PKI. In the early days of the Internet, every host had to maintain a list of every other host; the Domain Name System (DNS) introduced the idea of a distributed database for this purpose and the DNS is one of the key reasons that the Internet has grown 1 Form Proposal - Invoice 1.5 crack serial keygen it has. A PKI will fill a similar void in the e-commerce and PKC realm.

While certificates and the benefits of a PKI are most often associated with electronic commerce, the applications for PKI are 1 Form Proposal - Invoice 1.5 crack serial keygen broader and include secure electronic mail, payments and electronic checks, Electronic Data Interchange (EDI), secure transfer of Domain Name System (DNS) and routing information, electronic 1 Form Proposal - Invoice 1.5 crack serial keygen, and digitally signed documents. A single "global PKI" is still many years away, that is the ultimate goal of today's work Minecraft 1.8 (PC) Crackeado [PT-BR] | Download Torrent international electronic commerce changes the way in which we do business in a similar way in which the Internet has changed the way in which we communicate.

5. CRYPTOGRAPHIC ALGORITHMS IN ACTION

The paragraphs above have provided an overview of the different types of cryptographic algorithms, as well as some examples of some available protocols and schemes, 1 Form Proposal - Invoice 1.5 crack serial keygen. Table 3 provides a list of some other noteworthy schemes and cryptosystems employed — or proposed — for a variety of functions, most notably electronic commerce and secure communication. The paragraphs below will show several real cryptographic applications that many of us employ (knowingly or not) everyday for password protection and private communication. Some of the schemes described below never were widely deployed but are still historically interesting, thus remain included here. This list is, by no means, exhaustive but describes items that are of significant current and/or historic importance (a subjective judgement, to be sure).

BitmessageA decentralized, encrypted, peer-to-peer, trustless communications protocol for message exchange. The decentralized design, outlined in "Bitmessage: A Peer-to-Peer Message Authentication and Delivery System" (Warren, 2012), is conceptually based on the Bitcoin model.
CapstoneA now-defunct U.S. National Institute of Standards and Technology (NIST) and National Security Agency (NSA) project under the Bush Sr. and Clinton administrations for publicly available strong cryptography with keys escrowed by the government (NIST and the Treasury Dept.), 1 Form Proposal - Invoice 1.5 crack serial keygen. Capstone included one or more tamper-proof computer chips for implementation (Clipper), a secret key encryption algorithm (Skipjack), digital signature algorithm (DSA), key exchange algorithm (KEA), and hash algorithm (SHA).
Challenge-Handshake Authentication Protocol (CHAP)An authentication scheme that allows one party to prove who they are to a second party by demonstrating knowledge of a shared secret without actually divulging that shared secret to a third party who might be listening. Described in RFC 1994.
Chips-Message Robust Authentication (CHIMERA)A scheme proposed for authenticating navigation data and the spreading code of civilian signals in the Global Positioning System (GPS). This is an anti-spoofing mechanism to protect the unencrypted civilian signals; GPS military signals are encrypted.
ClipperThe computer chip that would implement the Skipjack encryption scheme. The Clipper chip was to have had a deliberate backdoor so that material encrypted with this device would not be beyond the government's reach. Described in 1993, Clipper was dead by 1996. See also EPIC's The Clipper Chip Web page.
Cryptography Research and Evaluation Committees (CRYPTEC)Similar in concept to the NIST AES process and NESSIE, CRYPTEC is the Japanese government's process to evaluate algorithms submitted for government and industry applications. CRYPTEX maintains a list of public key and secret key ciphers, hash functions, MACs, and other crypto algorithms approved for various applications in government environments.
Derived Unique Key Per Transaction (DUKPT)A key management scheme used for debit and credit card verification with point-of-sale (POS) transaction systems, automated teller machines (ATMs), and other financial applications. In DUKPT, a unique key is derived for each transaction based upon a fixed, shared key in such a way that knowledge of one derived key does not easily yield knowledge of other keys (including the fixed key). Therefore, if one of the derived keys is compromised, neither past nor subsequent transactions are endangered. DUKPT is specified in American National Standard (ANS) ANSI X9.24-1:2009 (Retail Financial Services Symmetric Key Management Part 1: Using Symmetric Techniques) and can be purchased at the ANSI X9.24 Web page.
ECRYPT Stream Cipher Project (eSTREAM)The eSTREAM project came about as a result of the failure of the NESSIE project to produce a stream cipher that survived cryptanalysis. eSTREAM ran from 2004 to 2008 with the primary purpose of promoting the design of efficient and compact stream ciphers. As of September 2008, the eSTREAM suite contains seven sciphers.
Escrowed Encryption Standard (EES)Largely unused, a controversial crypto scheme employing the SKIPJACK secret key crypto algorithm and a Law Enforcement Access Field (LEAF) 1 Form Proposal - Invoice 1.5 crack serial keygen method. LEAF was one part of the key escrow system crack office 2019 Archives allowed for decryption of ciphertext messages that had been intercepted by law enforcement agencies. Described more in FIPS PUB 185 (archived; no longer in force).
Federal Information Processing Standards (FIPS)These computer security- and crypto-related FIPS PUBs are produced by the U.S. National Institute of Standards and Technology (NIST) as standards for the U.S. Government. Current Federal Information Processing Standards (FIPS) related to crytography include:
FortezzaA PCMCIA card developed by NSA that implements 1 Form Proposal - Invoice 1.5 crack serial keygen Capstone algorithms, intended for use with the Defense Messaging Service (DMS). Originally called Tessera.
GOSTGOST is a family of algorithms defined in the Russian cryptographic standards. Although most of the specifications are written in Russian, a series of RFCs describe some of the aspects so that the algorithms can be used effectively in Internet applications:
  • RFC 4357: Additional Cryptographic Algorithms for Use with GOST 28147-89, GOST R 34.10-94, GOST R 34.10-2001, and GOST R 34.11-94 Algorithms
  • RFC 4490: Using the GOST 28147-89, GOST R 34.11-94, 1 Form Proposal - Invoice 1.5 crack serial keygen, GOST R 34.10-94, and GOST R 34.10-2001 Algorithms with Cryptographic Message Syntax (CMS)
  • RFC 4491: Using the GOST R 34.10-94, GOST R 34.10-2001, and GOST R 34.11-94 Algorithms with the Internet X.509 Public Key Infrastructure Certificate and CRL Profile
  • RFC 5830: GOST 28147-89: Encryption, Decryption, and Message Authentication Code (MAC) Algorithms
  • RFC 6986: GOST R 34.11-2012: Hash Function Algorithm
  • RFC 7091: GOST R 34.10-2012: Digital Signature Algorithm (Updates RFC 5832: GOST R 34.10-2001)
  • RFC 7801: GOST R 34.12-2015: Block Cipher "Kuznyechik"
  • RFC 7836: Guidelines on the Cryptographic Algorithms to Accompany the Usage of Standards GOST R 34.10-2012 and GOST R 34.11-2012
  • RFC 8891: GOST R 34.12-2015: Block Cipher "Magma"
IP Security (IPsec)The IPsec protocol suite is used to provide privacy and authentication services at the IP layer. An overview of the protocol suite and of the documents comprising IPsec can be found in RFC 2411. Other documents include:
  • RFC 4301: IP security architecture.
  • RFC 4302: IP Authentication Header (AH), one of the two primary IPsec functions; AH provides connectionless integrity and data origin authentication for IP datagrams and protects against replay attacks.
  • RFC 4303: IP Encapsulating Security Payload (ESP), the other primary IPsec function; ESP provides a variety of security services within IPsec.
  • RFC 4304: Extended Sequence Number (ESN) Addendum, allows for negotiation of a 32- or 64- bit sequence number, used to detect replay attacks.
  • RFC 4305: Cryptographic algorithm implementation requirements for ESP and AH.
  • RFC 5996: The Internet Key Exchange (IKE) protocol, version 2, 1 Form Proposal - Invoice 1.5 crack serial keygen for mutual authentication and establishing and maintaining security associations.
    • IKE v1 was described in three separate documents, RFC 2407 (application of ISAKMP to IPsec), RFC 2408 (ISAKMP, a framework for key management and security associations), and RFC 2409 (IKE, using part of Oakley and part of SKEME in conjunction with ISAKMP to obtain authenticated keying material for use with ISAKMP, and for other security associations such as AH and ESP). IKE v1 is obsoleted with the introduction Hentai Come See Me Tonight Full Crack IKEv2.
  • RFC 4307: Cryptographic algorithms used with IKEv2.
  • RFC 4308: Crypto suites for IPsec, IKE, and IKEv2.
  • RFC 4309: The use of AES in CBC-MAC mode with IPsec ESP.
  • RFC 4312: The use of the Camellia cipher algorithm in IPsec.
  • RFC 4359: The Use of RSA/SHA-1 Signatures within Encapsulating Security Payload (ESP) and Authentication Header (AH).
  • RFC 4434: Describes AES-XCBC-PRF-128, a pseudo-random function derived from the AES for use with IKE.
  • RFC 2403: Describes use of the HMAC with MD5 algorithm for data origin authentication and integrity protection in both AH and ESP.
  • RFC 2405: Describes use of DES-CBC (DES in Cipher Block Chaining Mode) for confidentiality in ESP.
  • RFC 2410: Defines use of the NULL encryption algorithm (i.e., provides authentication and integrity without confidentiality) in ESP.
  • RFC 2412: Describes OAKLEY, a key determination and distribution protocol.
  • RFC 2451: Describes use of Cipher Block Chaining (CBC) mode cipher algorithms with ESP.
  • RFCs 2522 and 2523: Description of Photuris, a session-key management protocol for IPsec.

In addition, RFC 6379 describes Suite B Cryptographic Suites for IPsec and RFC 6380 describes the Suite B profile for IPsec.

IPsec was first proposed for use with IP version 6 (IPv6), but can also be employed with the current IP version, IPv4.

(See more detail about IPsec below in Section 5.6.)

Internet Security Association and Key Management Protocol (ISAKMP/OAKLEY)ISAKMP/OAKLEY provide an infrastructure for Internet secure communications. ISAKMP, designed by the National Security Agency (NSA) and described in RFC 2408, is a framework for key management and security associations, independent of the key generation and cryptographic algorithms actually employed. The OAKLEY Key Determination Protocol, described in RFC 2412, is a key determination and distribution protocol using a variation of Diffie-Hellman.
KerberosA secret key encryption and authentication system, designed to authenticate requests for network resources within a user domain rather than to authenticate messages. Kerberos also uses a trusted third-party approach; a client communications with the Kerberos server to obtain "credentials" so that it may access services at the application server. Kerberos V4 used DES to generate keys and encrypt messages; Kerberos V5 uses DES and other schemes for key generation.

Microsoft added support for Kerberos V5 — with some proprietary extensions — in Windows 2000 Active 1 Form Proposal - Invoice 1.5 crack serial keygen. There are many Kerberos articles posted at Microsoft's Knowledge Base, notably "Kerberos Explained."
Keyed-Hash Message Authentication Code (HMAC)A message authentication scheme based upon secret key cryptography and the secret key shared between two parties rather than public key methods. Described in FIPS PUB 198 and RFC 2104. (See Section 5.19 below for details on HMAC operation.)
Message Digest Cipher (MDC)Invented by Peter Gutman, MDC turns a one-way hash function into a block cipher.
MIME Object Security Services (MOSS)Designed as a successor to PEM to provide PEM-based security services to MIME messages. Described in RFC 1848. Never widely implemented and now defunct.
Mujahedeen SecretsA Windows GUI, PGP-like cryptosystem. Developed by supporters of Al-Qaeda, the program employs the five finalist AES algorithms, namely, MARS, RC6, Rijndael, Serpent, and Twofish. Also described in Inspire Magazine, Issue 1, pp. 41-44 and Inspire Magazine, Issue 2, pp. 58-59. Additional related information can also be found in "How Al-Qaeda Uses Encryption Post-Snowden (Part 2)."
New European Schemes for Signatures, Integrity and Encryption (NESSIE)NESSIE was an independent project meant to augment the work of NIST during the AES adoption process by putting out an open call for new cryptographic primitives. The NESSIE project ran from about 2000-2003. While several new block ciper, PKC, MAC, 1 Form Proposal - Invoice 1.5 crack serial keygen, and digital signature algorithms were found during the NESSIE process, no new stream cipher survived cryptanalysis. As a result, the ECRYPT Stream Cipher Project (eSTREAM) was created.
NSA Suite B CryptographyAn NSA standard for securing information at the SECRET level. Defines use of:
  • Advanced Encryption Standard (AES) with key sizes of 128 and 256 bits, per FIPS PUB 197 for encryption
  • The Ephemeral Unified Model and the One-Pass Diffie Hellman (referred to as ECDH) using the curves with 256 and 384-bit prime moduli, per NIST Special Publication 800-56A for key exchange
  • Elliptic Curve Digital Signature Algorithm (ECDSA) using the curves with 256 and 384-bit prime moduli, per FIPS PUB 186-3 for digital signatures
  • Secure Hash Algorithm (SHA) using 256 and 384 bits, per FIPS PUB 180-3 for hashing

RFC 6239 describes Suite B Cryptographic Suites for Secure Shell (SSH) and RFC 6379 describes Suite B Cryptographic Suites for Secure IP (IPsec).

RFC 8423 reclassifies the RFCs related to the Suite B cryptographic algorithms as Historic, and it discusses the reasons for doing so.

Pretty Good Privacy (PGP)A family of cryptographic routines for e-mail, file, and disk encryption developed by Philip Zimmermann. PGP 2.6.x uses RSA for key management and digital signatures, IDEA for message encryption, and MD5 for computing the message's hash value; more information can also be found in RFC 1991. PGP 5.x (formerly known as "PGP 3") uses Diffie-Hellman/DSS for key management and digital signatures; IDEA, CAST, or 3DES for message encryption; and MD5 or SHA 1 Form Proposal - Invoice 1.5 crack serial keygen computing the message's hash value. OpenPGP, described in RFC 2440, is an open definition of security software based on PGP 5.x. The GNU Privacy Guard (GPG) is a free software version of OpenPGP.

(See more detail about PGP below in Section 5.5.)

Privacy Enhanced Mail (PEM)An IETF standard for secure electronic mail over the Internet, including provisions for encryption (DES), authentication, and key management (DES, RSA). Developed by the IETF but never widely used. Described in the following RFCs:
  • RFC 1421: Part I, Message Encryption and Authentication Procedures
  • RFC 1422: Part II, Certificate-Based Key Management
  • RFC 1423: Part III, Algorithms, Modes, and Identifiers
  • RFC 1424: Part IV, Key Certification and Related Services
Private Communication Technology (PCT)Developed by Microsoft for secure communication on the Internet. PCT supported Diffie-Hellman, Fortezza, and RSA for key establishment; DES, RC2, RC4, and triple-DES for encryption; and DSA and RSA message signatures. Never widely used; superceded by SSL and TLS.
Secure Electronic Transaction (SET)A communications protocol for securing credit card transactions, developed by MasterCard and VISA, in cooperation with IBM, Microsoft, RSA, and other companies. Merged two other protocols: Secure Electronic Payment Protocol (SEPP), an open specification for secure bank card transactions over the Internet developed by CyberCash, GTE, IBM, MasterCard, and Netscape; and Secure Transaction Technology (STT), a secure payment protocol developed by Microsoft and Visa International. Supports DES and RC4 1 Form Proposal - Invoice 1.5 crack serial keygen encryption, and RSA for signatures, key exchange, and public key encryption of bank card numbers. SET V1.0 is described in Book 1, Book 2, and Book 3. SET has been superceded by SSL and TLS.
Secure Hypertext Transfer Protocol (S-HTTP)An extension to HTTP to provide secure exchange of documents over the World Wide Web. Supported algorithms include RSA and Kerberos for key exchange, 1 Form Proposal - Invoice 1.5 crack serial keygen, DES, IDEA, RC2, and Triple-DES for encryption. Described in RFC 2660. S-HTTP was never as widely used as HTTP over SSL (https).
Secure Multipurpose Internet Mail Extensions (S/MIME)An IETF secure e-mail scheme superceding PEM, and adding digital signature and encryption capability to Internet MIME messages. S/MIME 1 Form Proposal - Invoice 1.5 crack serial keygen 3.1 is described in RFCs 3850 and 3851, and employs the Cryptographic Message Syntax described in RFCs 3369 and 3370.

(More detail about S/MIME can be found below in Section 5.15.)
Secure Sockets Layer (SSL)Developed in 1995 by Netscape Communications to provide application-independent security and privacy over the Internet. SSL is designed so that protocols such as HTTP, FTP (File Transfer Protocol), and Telnet can operate over it transparently. SSL allows both server authentication (mandatory) and client authentication (optional). RSA is used during negotiation to exchange keys and identify the actual cryptographic algorithm (DES, IDEA, RC2, RC4, or 3DES) to use for the session. SSL also uses MD5 for message digests and X.509 public key certificates. SSL was found to be breakable soon after the IETF announced formation of group to work on TLS and RFC 6176 specifically prohibits the use of SSL v2.0 by TLS clients. SSL version 3.0 is described in RFC 6101. All versions of SSL are now deprecated in favor of TLS; TLS v1.0 is sometimes referred to as "SSL v3.1."

(More detail about SSL can be found below in Section 5.7.)
Server Gated Cryptography (SGC)Microsoft extension to SSL that provided strong encryption for online banking and other financial applications using RC2 (128-bit key), RC4 (128-bit key), DES (56-bit key), or 3DES (equivalent of 168-bit key). Use of SGC required an Windows NT Server running Internet Information Server (IIS) 4.0 with a valid SGC certificate. SGC was available in 32-bit Windows versions of Internet Explorer (IE) 4.0; support for Mac, 1 Form Proposal - Invoice 1.5 crack serial keygen, Unix, and 16-bit Windows versions of IE was planned, but never materialized, and SGC was made moot when browsers started to ship with 128-bit encryption.
ShangMi (SM) Cipher SuitesA suite of authentication, encryption, and hash algorithms from the People's Republic of China.
  • SM2 Cryptography Algorithm: A public key crypto scheme based on elliptic curves. An overview of the specification, in Chinese, can be found in GM/T 0009-2012. Additional specifications can be found in:
  • SM3 Cryptographic Hash Algorithm: A hash algorithm operating on 512-bit blocks to produce a 256-bit hash value. Described in GB/T 32905-2016.
  • SM4 Block Cipher Algorithm: A Feistel block cipher algorithm with a block length and key length of 128 bits, and 32 rounds. Described in GB/T 32907-2016.
An application of the ShangMi Cipher Suites in TLS can be found in RFC 8998.
Signal ProtocolA protocol for providing end-to-end encryption for voice calls, video calls, and instant messaging (including group chats). Employing a combination of AES, ECC, and HMAC algorithms, it offers such features as confidentiality, integrity, authentication, forward/future secrecy, and message repudiation. Signal is particularly interesting because of its lineage and widespread use. The Signal Protocol's earliest versions were known as TextSecure, first developed by Open Whisper Systems in 2013. TextSecure itself was based on a 2004 protocol called Off-the-Record (OTR) Messaging, designed as an improvement over OpenPGP and S/MIME. TextSecure v2 (2014) introduced a scheme called the Axolotl Ratchet for key exchange and added additional communication features. After subsequent iterations improving key management (and the renaming of the key exchange protocol to Double Ratchet), additional cryptographic primitives, 1 Form Proposal - Invoice 1.5 crack serial keygen, and the addition of an encrypted voice calling application (RedPhone), TextSecure was renamed Signal Protocol in 2016. The Ratchet key exchange algorithm is at the heart of the power of this system. Most messaging apps employ the users' public and private keys; the weakness here is that if the phone falls into someone else's hands, all of the messages on the device — including deleted messages — can be decrypted, 1 Form Proposal - Invoice 1.5 crack serial keygen. The Ratchet algorithm generates a set of so-called "temporary keys" for each user, based upon that user's public/private key pair. When two users exchange messages, the Signal protocol creates a secret key by combining the temporary and permanent pairs of public and private keys for both users. Each message is assigned its own secret key. Because the generation of the secret key requires access to both users' private keys, it exists only on their two devices. The Signal Protocol is/has been employed in:
  • WhatsApp (introduced 2014)
  • G Data Software's Secure Chat (introduced 2015; service discontinued 2018)
  • Google's Allo app (introduced 2016; discontinued in favor of Messages app, 2019)
  • Facebook Messenger (introduced 2016)
  • Skype's Private Conversations mode (introduced 2018)
  • All of Google's Rich Communication Services (RCS) on Android systems (introduced 2020)
A reasonably good writeup of the protocol can be found in "Demystifying the Signal Protocol for End-to-End Encryption (E2EE)" by Kozhukhovskaya, Mora, and Wong (2017).
Simple Authentication and Security Layer (SASL)A framework for providing authentication and data security services in connection-oriented protocols FastStone Capture 9.7 + Portable Full Version la TCP), described in RFC 4422. It provides a structured interface and allows new protocols to reuse existing authentication mechanisms and allows old protocols to make use of new mechanisms.

It has been common practice on the Internet to permit anonymous access to various services, employing a plain-text password using a user name of "anonymous" and a password of an email address or some other identifying information. New IETF protocols disallow plain-text logins. The Anonymous SASL Mechanism (RFC 4505) provides a method for anonymous logins within the SASL framework.
Simple Key-Management for Internet Protocol (SKIP)Key management scheme for secure IP communication, specifically for IPsec, 1 Form Proposal - Invoice 1.5 crack serial keygen, and designed by Aziz and Diffie. SKIP essentially defines a public key infrastructure for the Internet and even uses X.509 certificates. Most public key cryptosystems assign keys on a per-session basis, 1 Form Proposal - Invoice 1.5 crack serial keygen, which is inconvenient 1 Form Proposal - Invoice 1.5 crack serial keygen the Internet since IP is connectionless. Instead, SKIP provides a basis for secure communication between any pair of Internet hosts. SKIP can employ DES, 3DES, IDEA, RC2, RC5, MD5, and SHA-1. As it happened, SKIP was not adopted for IPsec; IKE was selected instead.
SM9Chinese Standard GM/T0044-2016 SM9 (2016) is the Chinese national standard for Identity Based Cryptography. SM9 comprises three cryptographic algorithms, namely the Identity Based Digital Signature Algorithm, Identity Based Key Agreement Algorithm, and Identity Based Key Encapsulation Algorithm (allowing one party to securely send a symmetric key to another party). The SM9 scheme is also described in The SM9 Cryptographic Schemes (Z. Cheng).
TelegramTelegram, launched in 2013, is a cloud-based instant messaging and voice over IP (VoIP) service, with client app software available for all major computer and mobile device operating systems. Telegram allows users to exchange messages, photos, videos, etc., and supplies end-to-end encryption using a protocol called MTProto. stickers, audio and files of any type. MTProto employs 256-bit AES, 2048-bit RSA, and Diffie-Hellman key exchange. There have been several contriversies with Telegram, not the least of which has to do with the nationality of the founders and the true location of the business, as well as some operation issues. From a cryptological viewpoint, however, one 1 Form Proposal - Invoice 1.5 crack serial keygen tale can be found in "On the CCA (in)security of MTProto" (Jakobsen & Orlandi, 2015), who describe some of the crypto weaknesses of the protocol; specifically, that "MTProto does not satisfy the definitions of authenticated encryption (AE) or indistinguishability under chosen-ciphertext attack (IND-CCA)" (p. 1).
Transmission Control Protocol (TCP) encryption (tcpcrypt)As of 2019, the majority of Internet TCP traffic is not encrypted. The two primary reasons for this are (1) many legacy protocols have no mechanism with which to employ encryption (e.g., without a command such as STARTSSL, the protocol cannot invoke use of any encryption) and (2) many legacy applications cannot be upgraded, so no new encryption can be added. The response from 1 Form Proposal - Invoice 1.5 crack serial keygen IETF's TCP Increased Security Working Group was to define a transparent way within the transport layer (i.e., TCP) with which to invoke encryption. The TCP Encryption Negotiation Option (TCP-ENO) addresses these two problems with an out-of-band, fully backward-compatible TCP option with which to negotiate use of encryption. TCP-ENO is described in RFC 8547 and tcpcrypt, an encryption protocol to protect TCP streams, is described in RFC 8548.
Transport Layer Security (TLS)TLS v1.0 is an IETF specification (RFC 2246) intended to replace SSL v3.0. TLS v1.0 employs Triple-DES (secret key cryptography), SHA (hash), Diffie-Hellman (key exchange), and DSS (digital signatures), 1 Form Proposal - Invoice 1.5 crack serial keygen. TLS v1.0 was vulnerable to attack and updated by v1.1 (RFC 4346), which is now classified as an HISTORIC specification. TLS v1.1 was replaced by TLS v1.2 (RFC 5246) and, subsequently, by v1.3 (RFC 8446).

TLS is designed to operate over TCP. The IETF developed the Datagram Transport Layer Security (DTLS) protocol to operate over UDP. DTLS v1.2 is described in RFC 6347.

(See more detail about TLS below in Section 5.7.)
TrueCryptOpen source, 1 Form Proposal - Invoice 1.5 crack serial keygen, multi-platform cryptography software that can be used to encrypt a file, partition, or entire disk. One of TrueCrypt's more interesting features is that of plausible deniability with hidden volumes or hidden operating systems. The original Web site, truecrypt.org, suddenly went dark in May 2014. The current fork of TrueCrypt is VeraCrypt.

(See more detail about TrueCrypt below in Section 5.11.)
X.509ITU-T recommendation for the format of certificates for the public key infrastructure. Certificates map (bind) a user identity to a public key. The IETF application of X.509 certificates is documented in RFC 5280. An Internet X.509 Public Key Infrastructure is further defined in RFC 4210 (Certificate Management Protocols) and RFC 3647 (Certificate Policy and Certification Practices Framework).

5.1. Password Protection

Nearly all modern multiuser computer and network operating systems employ passwords at the very least to protect and authenticate users accessing computer and/or network resources. But passwords are not typically kept on a host or server in plaintext, but are generally encrypted using some sort of hash scheme.

A) /etc/passwd file root:Jbw6BwE4XoUHo:0:0:root:/root:/bin/bash carol:FM5ikbQt1K052:502:100:Carol Monaghan:/home/carol:/bin/bash alex:LqAi7Mdyg/HcQ:503:100:Alex Insley:/home/alex:/bin/bash gary:FkJXupRyFqY4s:501:100:Gary Kessler:/home/gary:/bin/bash todd:edGqQUAaGv7g6:506:101:Todd Pritsky:/home/todd:/bin/bash josh:FiH0ONcjPut1g:505:101:Joshua Kessler:/home/webroot:/bin/bash B.1) /etc/passwd file (with shadow passwords) root:x:0:0:root:/root:/bin/bash carol:x:502:100:Carol Monaghan:/home/carol:/bin/bash alex:x:503:100:Alex Insley:/home/alex:/bin/bash gary:x:501:100:Gary Kessler:/home/gary:/bin/bash todd:x:506:101:Todd Pritsky:/home/todd:/bin/bash josh:x:505:101:Joshua Kessler:/home/webroot:/bin/bash B.2) /etc/shadow file root:AGFw$1$P4u/uhLK$l2.HP35rlu65WlfCzq:11449:0:99999:7::: carol:kjHaN%35a8xMM8a/0kMl1?fwtLAM.K&kw.:11449:0:99999:7::: alex:1$1KKmfTy0a7#3.LL9a8H71lkwn/.hH22a:11449:0:99999:7::: gary:9ajlknknKJHjhnu7298ypnAIJKL$Jh.hnk:11449:0:99999:7::: todd:798POJ90uab6.k$klPqMt%alMlprWqu6$.:11492:0:99999:7::: josh:Awmqpsui*787pjnsnJJK%aappaMpQo07.8:11492:0:99999:7:::

FIGURE 8: Sample entries in Unix/Linux password files.

Unix/Linux, for example, uses a well-known hash via its crypt() function. Passwords are stored in the /etc/passwd file (Figure 8A); each record in the file contains the username, hashed password, user's individual and group numbers, user's name, home directory, and shell program; these fields are separated by colons (:). Note that each password is stored as a 13-byte string. The first two characters are actually a salt, randomness added to each password so that if two users have the same password, they will still be encrypted differently; the salt, in fact, provides a means so that a single password might have 4096 different encryptions. The remaining 11 bytes are the password hash, calculated using DES.

As it happens, the /etc/passwd file is world-readable on Unix systems. This fact, coupled with the weak encryption of the passwords, resulted in the development of the shadow password system where passwords are kept in a separate, non-world-readable file used in conjunction with the normal password file. When shadow passwords are used, the password entry in /etc/passwd is replaced with a "*" or "x" (Figure 8B.1) and the MD5 hash of the passwords are stored in /etc/shadow along with some other account information (Figure 8B.2).

Windows NT uses a similar scheme to store passwords in the Security Access Manager (SAM) file. In the NT case, all passwords are hashed using the MD4 algorithm, resulting in a 128-bit (16-byte) hash value (they are then obscured using an undocumented mathematical transformation that was a secret until distributed on the Internet). The password password, for example, might be stored as the hash value (in hexadecimal) 60771b22d73c34bd4a290a79c8b09f18.

Passwords are not saved in plaintext on computer systems precisely so they cannot be easily compromised. For similar reasons, we don't want passwords sent in plaintext across a network. But for remote logon applications, how does a client system identify itself or a user to the server? One mechanism, 1 Form Proposal - Invoice 1.5 crack serial keygen, of course, is to send the password as a hash value and that, indeed, may be done. A weakness of that approach, however, is that an intruder can grab the password off of the network and use an off-line attack (such as a dictionary attack where an attacker takes every known word and encrypts it with the network's encryption algorithm, hoping eventually to find a match with a purloined password hash). In some situations, an attacker only has to copy the hashed password value and use it later on to gain unauthorized entry without ever learning the actual password.

An even stronger authentication method uses the password to modify a shared secret between the client and server, but never allows the password in any form to go across the network. This is the basis for the Challenge Handshake Authentication Protocol (CHAP), the remote logon process used by Windows NT.

As suggested above, Windows NT passwords are stored in a security file on a server as a 16-byte hash value. In truth, Windows NT stores two hashes; a weak hash based upon the old LAN Manager (LanMan) scheme and the newer NT hash. When a user logs on to a server from a remote workstation, the user is identified by the username, sent across the network in plaintext (no worries here; it's not a secret anyway!). The server then generates a 64-bit random number and sends it to the client (also in plaintext). This number is the challenge.

Using the LanMan scheme, the client system then encrypts the challenge using DES. Recall that DES employs a 56-bit key, acts on a 64-bit block of data, and produces a 64-bit output. In this case, the 64-bit data block is the random number. The client actually uses three different DES keys to encrypt the random number, producing three different 64-bit outputs. The first key is the first seven bytes (56 bits) of the password's hash value, the second key is the next seven bytes in the password's hash, and the third key is the remaining two bytes of the password's hash concatenated with five zero-filled bytes. (So, for the example above, the three DES keys would be 60771b22d73c34, bd4a290a79c8b0, and 9f180000000000.) Each key is applied to the random number resulting in three 64-bit outputs, which comprise the response. Thus, the server's 8-byte challenge yields a 24-byte response from the client and this is all that would be seen on the network. The server, for its part, does the same calculation to ensure that the values match.

There is, however, a significant weakness to this system. Specifically, the response is generated in such a way as to effectively reduce 16-byte hash to three smaller hashes, of length seven, seven, and two, respectively. Thus, a password cracker has to break at most a 7-byte hash. One Windows NT vulnerability test program that I used in the past reported passwords that were "too short," defined as "less than 8 characters." When I asked how the program knew that passwords were too short, the software's salespeople suggested to me that the program broke the passwords to determine their length. This was, in fact, not the case at all; all the software really had to do was to look at the last eight bytes of the Windows NT LanMan hash to see that the password was seven or fewer characters.

Consider the following example, showing the LanMan hash of two different short passwords (take a close look at the last 8 bytes):

AA: 89D42A44E77140AAAAD3B435B51404EE
AAA: 1C3A2B6D939A1021AAD3B435B51404EE

Note that the NT hash provides no such clue:

AA: C5663434F963BE79C8FD99F535E7AAD8
AAA: 6B6E0FB2ED246885B98586C73B5BFB77

It is worth noting that the discussion above describes the Microsoft version of CHAP, or MS-CHAP (MS-CHAPv2 is described in RFC 2759). MS-CHAP assumes that it is working with hashed values of the password as the key to encrypting the challenge. More traditional CHAP (RFC 1994) assumes that it is starting with passwords in plaintext. The relevance of this observation is that a CHAP client, for example, cannot be authenticated by an MS-CHAP server; both client and server must use the same CHAP version.

5.2. Diffie-Hellman Key Exchange

Diffie and Hellman introduced the concept of public key cryptography. The mathematical "trick" of Diffie-Hellman key exchange is that it is relatively easy to compute exponents compared to computing discrete logarithms. Diffie-Hellman allows two parties — the ubiquitous Alice and Bob — 1 Form Proposal - Invoice 1.5 crack serial keygen generate a secret key; they need to exchange some information over an unsecure communications channel to perform the calculation but an eavesdropper cannot determine the shared secret key based upon this information.

Diffie-Hellman works like this. Alice and Bob start by agreeing on a large prime number, N. They also have to choose some number G so that G<N.

There is actually another constraint on G, namely that it must be primitive with respect to N. Primitive is a definition that is a little beyond the scope of our discussion but basically G is primitive to N if the set of N-1 values of Gi mod N for i = (1,N-1) are all different. As an example, 2 is not primitive to 7 because the set of powers of 2 from 1 to 6, mod 7 (i.e., 21 mod 7, 22 mod 7. ., 26 mod 7) = {2,4,1,2,4,1}. On the other hand, 1 Form Proposal - Invoice 1.5 crack serial keygen, 3 is primitive to 7 because the set of powers of 3 from 1 to 6, mod 7 = {3,2,6,4,5,1}.

(The definition of primitive introduced a new term to some readers, namely mod. The phrase x mod y (and read as written!) means "take the remainder after dividing x by y." Thus, 1 mod 7 = 1, 9 mod 6 = 3, and 8 mod 8 = 0. Read more about the modulo function in the appendix.)

Anyway, either Alice or Bob selects N and G; they then tell the other party what the values are. Alice and Bob then work independently (Figure 9):

Alice.

  1. Choose a large random number, XA < N. This is Alice's private key.
  2. Compute YA = GXA mod N. This is Alice's public key.
  3. Exchange public key with Bob.
  4. Compute KA = YBXA mod N
Bob.

  1. Choose a large random number, XB < N. This is Bob's private key.
  2. Compute YB = GXB mod N. This is Bob's public key.
  3. Exchange public key with Alice.
  4. Compute KB = YAXB mod N
FIGURE 9: Diffie-Hellman key exchange model.

Note that XA and XB are kept secret while YA and YB are openly shared; these are the private and public keys, respectively. Based on their own private key and the public key learned from the other party, Alice and Bob have 1 Form Proposal - Invoice 1.5 crack serial keygen their secret keys, KA and KB, respectively, which are equal to GXAXB mod N.

Perhaps a small example will help here. Although Alice and Bob will really choose large values for N and G, I will use small values for example only; let's use N=7 and G=3, as shown in Figure 10.

Alice.

  1. Choose private key; XA = 2
  2. Compute public key; YA = 32 mod 7 = 2
  3. Exchange public key with Bob
  4. KA = YBXA mod N = 62 mod 7 = 1
Bob.

  1. Choose private key; XB = 3
  2. Compute public key; YB = 33 mod 7 = 6
  3. Exchange public key with Alice
  4. KB = YAXB mod N = 23 mod 7 = 1
FIGURE 10: Diffie-Hellman key exchange example.

In this example, then, Alice and Bob will both find the secret key 1 which is, indeed, 36 mod 7 (i.e., GXAXB = 32x3). If an eavesdropper (Eve) was listening in on the information exchange between Alice and Bob, she would learn G, N, YA, and YB which is a lot of information but insufficient to compromise the key; as long as XA and XB remain unknown, K is safe. As stated above, calculating Y = GX is a lot easier than finding X = logG Y.


A short digression on modulo arithmetic. In the paragraph above, we noted that 36 mod 7 1 Form Proposal - Invoice 1.5 crack serial keygen 1. This can be confirmed, 1 Form Proposal - Invoice 1.5 crack serial keygen, of course, by noting that:

36 = 729 = 104*7 + 1

There is a nice property of modulo arithmetic, however, that makes this determination a little easier, namely: (a mod x)(b mod x) = (ab mod x). Therefore, one possible shortcut is to note that 36 = (33)(33). Therefore, 36 mod 7 = (33 mod 7)(33 mod 7) = (27 mod 7)(27 mod 7) = 6*6 mod 7 = 36 mod 7 = 1.


Diffie-Hellman can also be used to allow key sharing amongst multiple users. Note again that the Diffie-Hellman algorithm is used to generate secret keys, not to encrypt and decrypt messages.

5.3. RSA Public Key Cryptography

Unlike Diffie-Hellman, RSA can be used for key exchange as well as digital signatures and the encryption of small blocks of data. Today, RSA is primarily used to encrypt the session key used for secret key encryption (message integrity) or the message's hash value (digital signature). RSA's mathematical hardness comes from the ease in calculating large numbers and the difficulty in finding the prime factors of those large numbers. Although employed with numbers using hundreds of digits, the math behind RSA is relatively straight-forward.

To create an RSA public/private key pair, here are the basic steps:

  1. Choose two prime numbers, p and q. From these numbers you can calculate the modulus, n = pq.
  2. Select a third number, e, that is relatively prime to (i.e., it does not divide evenly into) the product (p-1)(q-1). The number e is the public exponent.
  3. Calculate an integer d from the quotient (ed-1)/[(p-1)(q-1)]. The number d is the private exponent.

The public key is the number pair (n,e). Although these values are publicly known, it is computationally infeasible to determine d from n and e if p and q are large enough.

To encrypt a message, M, with the public key, create the ciphertext, C, using the equation:

The receiver then decrypts the ciphertext with the private key using the equation:

Now, this might look a bit complex and, 1 Form Proposal - Invoice 1.5 crack serial keygen, indeed, the mathematics does take a lot of computer power given the large size of the numbers; since p and q may be 100 digits (decimal) or more, d and e will be about the same size and n may be over 200 digits. Nevertheless, a simple example may help. In this example, the values for p, q, e, and d are purposely chosen to be very small and the reader will see exactly how badly these values perform, but hopefully 1 Form Proposal - Invoice 1.5 crack serial keygen algorithm will be adequately demonstrated:

  1. Select p=3 and q=5.
  2. The modulus n = pq = 15.
  3. The value e must be relatively prime to (p-1)(q-1) = (2)(4) = 8. Select e=11.
  4. The value d must be chosen so that (ed-1)/[(p-1)(q-1)] is an integer. Thus, the value (11d-1)/[(2)(4)] = (11d-1)/8 must be an integer. Calculate one possible value, d=3.
  5. Let's suppose that we want to send a message — HyperSnap 8.17.00 Crack Full Version Download a secret key — that has the numeric value of 7 (i.e., M=7). [More on this choice below.]
  6. The sender encrypts the message (M) using the public key value (e,n)=(11,15) and computes the ciphertext (C) with the formula C = 711 mod 15 = 1977326743 mod 15 = 13.
  7. The receiver decrypts the ciphertext using the private key value (d,n)=(3,15) and computes the plaintext with the formula M = 133 mod 15 = 2197 mod 15 = 7.

I choose this trivial example because the value of n is so small (in particular, the value M cannot exceed n). But here is a more realistic example using larger d, e, and n values, as well as a more meaningful message; thanks to Barry Steyn for permission to use values from his How RSA Works With Examples page.

Let's say that we have chosen p and q so that we have the following value for n:

14590676800758332323018693934907063529240187237535716439958187
10198734387990053589383695714026701498021218180862924674228281
57022922076746906543401224889672472407926969987100581290103199
31785875366371086235765651050788371429711563734278891146353510
2712032765166518411726859837988672111837205085526346618740053

Let's also suppose that we have selected the public key, e, and private key, d, as follows:

65537

89489425009274444368228545921773093919669586065884257445497854
45648767483962981839093494197326287961679797060891728367987549
93315741611138540888132754881105882471930775825272784379065040
15680623423550067240042466665654232383502922215493623289472138
866445818789127946123407807725702626644091036502372545139713

Now suppose that our message (M) is the character string "attack at dawn" which has the numeric value (after converting the ASCII characters to a bit string and interpreting that bit string as a decimal number) of 1976620216402300889624482718775150.

The encryption phase uses the formula C = Me mod n, so C has the value:

35052111338673026690212423937053328511880760811579981620642802
34668581062310985023594304908097338624111378404079470419397821
53784997654130836464387847409523069325349451950801838615742252
26218879827232453912820596886440377536082465681750074417459151
485407445862511023472235560823053497791518928820272257787786

The decryption phase uses the formula M = Cd mod n, so M has the value that matches our original plaintext:

1976620216402300889624482718775150

This more realistic example gives just a clue as to how large the numbers are that are used in the real world implementations. RSA keylengths of 512 and 768 bits are considered to be pretty weak. The minimum suggested RSA key is 1024 bits; 2048 and 3072 bits are even better.

As an aside, Adam Back (http://www.cypherspace.org/~adam/) wrote a two-line Perl script to implement RSA. It employs dc, an arbitrary precision arithmetic package that ships with most UNIX systems:

print pack"C*",split/\D+/,`echo "16iII*o\[email protected]{$/=$z;[(pop,pop,unpack"H*",<> )]}\EsMsKsN0[lN*1lK[d2%Sa2/d0<X+d*lMLa^*lN%0]dsXx++lMlN/dsM0<J]dsJxp"

1 comments

  1. "It's taking up 11M of your hard drive." Sure, I bet storage size is your real reason to uninstall IE! 🤣🤣🤣

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