The SHA hash functions are five cryptographic hash functions designed by the National Security Agency (NSA) and published by the NIST as a U. A cryptographic Hash function is a transformation that takes an input (or 'message' and returns a fixed-size string which is called the hash value (sometimes The National Security Agency/ Central Security Service ( NSA/CSS) is a cryptologic intelligence agency of the United States government S. Federal Information Processing Standard. Federal Information Processing Standards ( FIPS) are publicly announced standards developed by the United States Federal government for use by all non-military SHA stands for Secure Hash Algorithm. Hash algorithms compute a fixed-length digital representation (known as a message digest) of an input data sequence (the message) of any length. They are called “secure” when:

1. It is computationally infeasible to find a message that corresponds to a given message digest.
2. It is computationally infeasible to find two different messages that produce the same message digest.
3. Any change to a message (including single bit changes) will, with an exceedingly high probability, result in a completely different message digest.

The five algorithms are denoted SHA-1, SHA-224, SHA-256, SHA-384, and SHA-512. The latter four variants are sometimes collectively referred to as SHA-2. SHA-1 produces a message digest that is 160 bits long; the number in the other four algorithms' names denote the bit length of the digest they produce.

SHA-1 is employed in several widely used security applications and protocols, including TLS and SSL, PGP, SSH, S/MIME, and IPsec. Transport Layer Security ( TLS) and its predecessor Secure Sockets Layer ( SSL) are Cryptographic protocols that provide secure Transport Layer Security ( TLS) and its predecessor Secure Sockets Layer ( SSL) are Cryptographic protocols that provide secure Pretty Good Privacy (PGP is a Computer program that provides Cryptographic Privacy and Authentication. Secure Shell or SSH is a Network protocol that allows data to be exchanged using a Secure channel between two networked devices S/MIME ( Secure / Multipurpose Internet Mail Extensions) is a standard for Public key Encryption and signing of E-mail encapsulated Internet Protocol Security ( IPsec) is a suite of protocols for securing Internet Protocol (IP communications by authenticating and/or encrypting It was considered to be the successor to MD5, an earlier, widely-used hash function. In Cryptography, MD5 ( Message-Digest algorithm 5) is a widely used partially insecure Cryptographic hash function with a 128- Bit hash value

The security of SHA-1 has been somewhat compromised by cryptography researchers. ^[1] Although no attacks have yet been reported on the SHA-2 variants, they are algorithmically similar to SHA-1 and so efforts are underway to develop improved alternative hashing algorithms. ^[2][3] An open competition for a new SHA-3 function was formally announced in the Federal Register on November 2, 2007. The Federal Register (since March 14, 1936) abbreviated Fed Reg ^[4] "NIST is initiating an effort to develop one or more additional hash algorithms through a public competition, similar to the development process for the Advanced Encryption Standard (AES). The Advanced Encryption Standard (AES the Block cipher ratified as a standard by National Institute of Standards and Technology of the United States (NIST was In Cryptography, the Advanced Encryption Standard ( AES) also known as Rijndael, is a Block cipher adopted as an Encryption "^[5] Submissions are due October 31, 2008 and the proclamation of a winner and publication of the new standard are scheduled to take place in 2012.

SHA-0 and SHA-1

One iteration within the SHA-1 compression function. A, B, C, D and E are 32-bit words of the state; F is a nonlinear function that varies; _n denotes a left bit rotation by n places; n varies for each operation. W_t is the expanded message word of round t, K_t is the round constant of round t denotes addition modulo 2³².

The original specification of the algorithm was published in 1993 as the Secure Hash Standard, FIPS PUB 180, by US government standards agency NIST (National Institute of Standards and Technology). Federal Information Processing Standards ( FIPS) are publicly announced standards developed by the United States Federal government for use by all non-military This version is now often referred to as SHA-0. It was withdrawn by NSA shortly after publication and was superseded by the revised version, published in 1995 in FIPS PUB 180-1 and commonly referred to as SHA-1. The National Security Agency/ Central Security Service ( NSA/CSS) is a cryptologic intelligence agency of the United States government SHA-1 differs from SHA-0 only by a single bitwise rotation in the message schedule of its compression function; this was done, according to NSA, to correct a flaw in the original algorithm which reduced its cryptographic security. In Cryptography, a one-way compression function is a function that transforms two fixed length inputs to an output of the same size as one of the inputs However, NSA did not provide any further explanation or identify the flaw that was corrected. Weaknesses have subsequently been reported in both SHA-0 and SHA-1. SHA-1 appears to provide greater resistance to attacks, supporting the NSA’s assertion that the change increased the security.

SHA-1 (as well as SHA-0) produces a 160-bit digest from a message with a maximum length of (2⁶⁴ − 1) bits and is based on principles similar to those used by Ronald L. Rivest of MIT in the design of the MD4 and MD5 message digest algorithms. A message in its most general meaning is an object of Communication. Ronald Linn Rivest (born 1947, Schenectady, New York) is a cryptographer. MD4 is a message digest Algorithm (the fourth in a series designed by Professor Ronald Rivest of MIT in 1990 In Cryptography, MD5 ( Message-Digest algorithm 5) is a widely used partially insecure Cryptographic hash function with a 128- Bit hash value

Cryptanalysis

For a hash function which violates the first criterion listed above, finding a message that corresponds to a given message digest can always be done using a brute force search in 2^L evaluations, where L is the number of bits in the message digest. This is called a preimage attack and may or may not be practical in a particular computing environment. In Cryptography, a preimage attack on a cryptographic hash is an attempt to find a message that has a specific hash value The second criterion, finding two different messages that produce the same message digest, known as a collision, requires on average only 2^L/2 evaluations using a birthday attack. A birthday attack is a type of cryptographic attack so named because it exploits the Mathematics behind the Birthday problem in Probability theory For the latter reason the strength of a hash function is usually compared to a symmetric cipher of half the message digest length. Thus SHA-1 was originally thought to have 80-bit strength.

Cryptographers have produced collision pairs for SHA-0 and have found algorithms that should produce SHA-1 collisions in far fewer than the originally expected 2⁸⁰ evaluations.

In terms of practical security, a major concern about these new attacks is that they might pave the way to more efficient ones. Whether this is the case has yet to be seen, but a migration to stronger hashes is believed to be prudent. Some of the applications that use cryptographic hashes, such as password storage, are only minimally affected by a collision attack. Constructing a password that works for a given account requires a preimage attack, as well as access to the hash of the original password (typically in the shadow file) which may or may not be trivial. Reversing password encryption (e. g. to obtain a password to try against a user's account elsewhere) is not made possible by the attacks.

In the case of document signing, an attacker could not simply fake a signature from an existing document—the attacker would have to produce a pair of documents, one innocuous and one damaging, and get the private key holder to sign the innocuous document. There are practical circumstances in which this is possible.

SHA-0

At CRYPTO 98, two French researchers, Florent Chabaud and Antoine Joux, presented an attack on SHA-0 (Chabaud and Joux, 1998): collisions can be found with complexity 2⁶¹, fewer than the 2⁸⁰ for an ideal hash function of the same size. "Crypto" is also an abbreviation for Cryptology, the subject of this conference In Computer science, a hash collision or hash clash is a situation that occurs when two distinct inputs into a Hash function produce identical outputs

In 2004, Biham and Chen found near-collisions for SHA-0 — two messages that hash to nearly the same value; in this case, 142 out of the 160 bits are equal. Eli Biham (אלי ביהם is an Israeli Cryptographer and cryptanalyst, currently a professor at the Technion Israeli Institute of Technology They also found full collisions of SHA-0 reduced to 62 out of its 80 rounds.

Subsequently, on 12 August 2004, a collision for the full SHA-0 algorithm was announced by Joux, Carribault, Lemuet, and Jalby. Events 1099 - First Crusade: Battle of Ascalon - Crusaders under the command of Godfrey of Bouillon defeat Fatimid "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again " This was done by using a generalization of the Chabaud and Joux attack. Finding the collision had complexity 2⁵¹ and took about 80,000 CPU hours on a supercomputer with 256 Itanium 2 processors. A supercomputer is a Computer that is at the frontline of processing capacity particularly speed of calculation (at the time of its introduction Itanium is the brand name for 64-bit Intel Microprocessors that implement the Intel Itanium architecture (formerly called IA-64)

On 17 August 2004, at the Rump Session of CRYPTO 2004, preliminary results were announced by Wang, Feng, Lai, and Yu, about an attack on MD5, SHA-0 and other hash functions. Events 986 - A Byzantine army was destroyed in the pass of Trajan's Gate by the Bulgarians under the Comitopuli "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again " Wang Xiaoyun ( (born 1966) is a researcher and professor in the Department of Mathematics and System Science Shandong University, Shandong, China In Cryptography, MD5 ( Message-Digest algorithm 5) is a widely used partially insecure Cryptographic hash function with a 128- Bit hash value The complexity of their attack on SHA-0 is 2⁴⁰, significantly better than the attack by Joux et al. ^[6][7]

In February 2005, an attack by Xiaoyun Wang, Yiqun Lisa Yin, and Hongbo Yu was announced which could find collisions in SHA-0 in 2³⁹ operations. ^[8][9]

SHA-1

In light of the results for SHA-0, some experts suggested that plans for the use of SHA-1 in new cryptosystems should be reconsidered. There are two different meanings of the word cryptosystem. One is used by the cryptographic community while the other is the meaning understood by the public After the CRYPTO 2004 results were published, NIST announced that they planned to phase out the use of SHA-1 by 2010 in favor of the SHA-2 variants. ^[10]

In early 2005, Rijmen and Oswald published an attack on a reduced version of SHA-1 — 53 out of 80 rounds — which finds collisions with a computational effort of fewer than 2⁸⁰ operations. Vincent Rijmen (born 16 October 1970, in Leuven, near Brussels, Belgium) is a Belgian Cryptographer and one of the designers ^[11]

In February 2005, an attack by Xiaoyun Wang, Yiqun Lisa Yin, and Hongbo Yu was announced. Wang Xiaoyun ( (born 1966) is a researcher and professor in the Department of Mathematics and System Science Shandong University, Shandong, China ^[12] The attacks can find collisions in the full version of SHA-1, requiring fewer than 2⁶⁹ operations. (A brute-force search would require 2⁸⁰ operations. In Computer science, brute-force search or exhaustive search, also known as generate and test, is a trivial but very general problem-solving technique )

The authors write: "In particular, our analysis is built upon the original differential attack on SHA0 [sic], the near collision attack on SHA0, the multiblock collision techniques, as well as the message modification techniques used in the collision search attack on MD5. Breaking SHA1 would not be possible without these powerful analytical techniques. "^[13]. The authors have presented a collision for 58-round SHA-1, found with 2³³ hash operations. The paper with the full attack description was published in August 2005 at the CRYPTO conference.

In an interview, Yin states that, "Roughly, we exploit the following two weaknesses: One is that the file preprocessing step is not complicated enough; another is that certain math operations in the first 20 rounds have unexpected security problems. "^[14]

On 17 August 2005, an improvement on the SHA-1 attack was announced on behalf of Xiaoyun Wang, Andrew Yao and Frances Yao at the CRYPTO 2005 rump session, lowering the complexity required for finding a collision in SHA-1 to 2⁶³. Events 986 - A Byzantine army was destroyed in the pass of Trajan's Gate by the Bulgarians under the Comitopuli Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. ^[15] On 18 December 2007 the details of this result were explained and verified by Martin Cochran. Events 218 BC - Second Punic War: Battle of the Trebia - Hannibal 's Carthaginian forces defeat those of the Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. ^[16]

Christophe De Cannière and Christian Rechberger further improved the attack on SHA-1 in "Finding SHA-1 Characteristics: General Results and Applications,"^[17] receiving the Best Paper Award at ASIACRYPT 2006. Asiacrypt (also ASIACRYPT) is an important international conference for Cryptography research Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. A two-block collision for 64-round SHA-1 was presented, found using unoptimized methods with 2³⁵ compression function evaluations.

As this attack requires the equivalent of about 2³⁵ evaluations, it is considered to be a significant theoretical break. ^[18] To find an actual collision, however, a massive distributed computing effort or very large parallel supercomputer such as those possessed by NSA would be required. The National Security Agency/ Central Security Service ( NSA/CSS) is a cryptologic intelligence agency of the United States government To that end, a collision search for SHA-1 using the distributed computing platform BOINC is currently being made by the Graz University of Technology. The Berkeley Open Infrastructure for Network Computing ( BOINC) is a non-commercial Middleware system for volunteer and Grid computing. Graz University of Technology (German "Technische Universität Graz" short "TU Graz" is (after University of Graz) the second largest university in ^[19]

At the Rump Session of CRYPTO 2006, Christian Rechberger and Christophe De Cannière claimed to have discovered a collision attack on SHA-1 that would allow an attacker to select at least parts of the message. ^[20][21]

SHA-2

A round of one of the SHA-2 variants (SHA-256)

NIST published four additional hash functions in the SHA family, each with longer digests, collectively known as SHA-2. However the term SHA-2 officially is not standardized.

The individual variants are named after their digest lengths (in bits): SHA-224, SHA-256, SHA-384, and SHA-512. The latter three were first published in 2001 in the draft FIPS PUB 180-2, at which time review and comment were accepted. FIPS PUB 180-2, which also includes SHA-1, was released as an official standard in 2002. In February 2004, a change notice was published for FIPS PUB 180-2, specifying an additional variant, SHA-224, defined to match the key length of two-key Triple DES. In Cryptography, Triple DES is a Block cipher formed from the Data Encryption Standard (DES Cipher by using it three times These variants are patented in US patent 6829355. The United States representing NSA, has released the patent under a royalty free license. The United States of America —commonly referred to as the ^[22]

SHA-256 and SHA-512 are novel hash functions computed with 32- and 64-bit words, respectively. They use different shift amounts and additive constants, but their structures are otherwise virtually identical, differing only in the number of rounds. SHA-224 and SHA-384 are simply truncated versions of the first two, computed with different initial values.

These new hash functions have not received as much scrutiny by the public cryptographic community as SHA-1 has, and so their cryptographic security is not yet as well-established. Gilbert and Handschuh (2003) have studied the newer variants and found no weaknesses. ^[23]

SHA sizes

In the table below, internal state means the “internal hash sum” after each compression of a data block; see Merkle-Damgård construction for more details.

Applications

For more details on this topic, see Cryptographic hash function#Applications. In Computer science, a hash collision or hash clash is a situation that occurs when two distinct inputs into a Hash function produce identical outputs A cryptographic Hash function is a transformation that takes an input (or 'message' and returns a fixed-size string which is called the hash value (sometimes

SHA-1, SHA-224, SHA-256, SHA-384, and SHA-512 are the secure hash algorithms required by law for use in certain U.  S. Government applications, including use within other cryptographic algorithms and protocols, for the protection of sensitive unclassified information. FIPS PUB 180-1 also encouraged adoption and use of SHA-1 by private and commercial organizations.

A prime motivation for the publication of the Secure Hash Algorithm was the Digital Signature Standard, in which it is incorporated. The Digital Signature Algorithm (DSA is a United States Federal Government standard or FIPS for Digital signatures It was proposed by the

The SHA hash functions have been used as the basis for the SHACAL block ciphers. In Cryptography, SHACAL-1 and SHACAL-2 are Block ciphers based on Cryptographic hash functions from the SHA family. In Cryptography, a block cipher is a symmetric key Cipher which operates on fixed-length groups of Bits termed blocks, with an

Example hashes

Main article: Examples of SHA digests

The following is an example of SHA-1 digests. The following are some examples of SHA digests. ASCII encoding is assumed for all messages ASCII encoding is assumed for all messages. American Standard Code for Information Interchange ( ASCII)

SHA1("The quick brown fox jumps over the lazy dog") 
 = 2fd4e1c6 7a2d28fc ed849ee1 bb76e739 1b93eb12

Even a small change in the message will, with overwhelming probability, result in a completely different hash due to the avalanche effect. " The quick brown fox jumps over the lazy dog " is a Panagram (a Phrase that uses all the letters of the Alphabet) that has been used to test This article is about Cryptography; for other meanings see Snowball effect and Avalanche (disambiguation. For example, changing dog to cog:

SHA1("The quick brown fox jumps over the lazy cog") 
 = de9f2c7f d25e1b3a fad3e85a 0bd17d9b 100db4b3

Official validation

Main article: CMVP

Implementations of all FIPS-approved security functions can be officially validated through the CMVP program, jointly run by the National Institute of Standards and Technology (NIST) and the Communications Security Establishment (CSE). The Cryptographic Module Validation Program ( CMVP) is a joint American and Canadian security accreditation program for cryptographic modules The Cryptographic Module Validation Program ( CMVP) is a joint American and Canadian security accreditation program for cryptographic modules The Communications Security Establishment Canada ( CSEC or CSE) (Centre de la sécurité des télécommunications Canada ( CSTC or CST) is For informal verification, a package to generate a high number of test vectors is made available for download on the NIST site; the resulting verification however does not replace in any way the formal CMVP validation, which is required by law for certain applications.

As of October 2006, there are more than 500 validated implementations of SHA-1, with fewer than ten of them capable of handling messages with a length in bits not a multiple of eight (see SHS Validation List). Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. It is also important to note that some implementations available on the Internet do not digest the NIST validation vectors correctly, although they may correctly process the examples listed in the SHA-1 standard.

SHA-1 algorithm

Pseudocode for the SHA-1 algorithm follows:

Note: All variables are unsigned 32 bits and wrap modulo 232 when calculating

Initialize variables:
h0 = 0x67452301
h1 = 0xEFCDAB89
h2 = 0x98BADCFE
h3 = 0x10325476
h4 = 0xC3D2E1F0

Pre-processing:
append the bit '1' to the message
append k bits '0', where k is the minimum number ≥ 0 such that the resulting message
    length (in bits) is congruent to 448 (mod 512)
append length of message (before pre-processing), in bits, as 64-bit big-endian integer

Process the message in successive 512-bit chunks:
break message into 512-bit chunks
for each chunk
    break chunk into sixteen 32-bit big-endian words w[i], 0 <= i <= 15

    Extend the sixteen 32-bit words into eighty 32-bit words:
    for i from 16 to 79
        w[i] = (w[i-3] xor w[i-8] xor w[i-14] xor w[i-16]) leftrotate 1

    Initialize hash value for this chunk:
    a = h0
    b = h1
    c = h2
    d = h3
    e = h4

    Main loop:
    for i from 0 to 79
        if 0 ≤ i ≤ 19 then
            f = (b and c) or ((not b) and d)
            k = 0x5A827999
        else if 20 ≤ i ≤ 39
            f = b xor c xor d
            k = 0x6ED9EBA1
        else if 40 ≤ i ≤ 59
            f = (b and c) or (b and d) or (c and d)
            k = 0x8F1BBCDC
        else if 60 ≤ i ≤ 79
            f = b xor c xor d
            k = 0xCA62C1D6

        temp = (a leftrotate 5) + f + e + k + w[i]
        e = d
        d = c
        c = b leftrotate 30
        b = a
        a = temp

    Add this chunk's hash to result so far:
    h0 = h0 + a
    h1 = h1 + b 
    h2 = h2 + c
    h3 = h3 + d
    h4 = h4 + e

Produce the final hash value (big-endian):
digest = hash = h0 append h1 append h2 append h3 append h4

Instead of the formulation from the original FIPS PUB 180-1 shown, the following equivalent expressions may be used to compute f in the main loop above:

(0  ≤ i ≤ 19): f = d xor (b and (c xor d))                (alternative 1)
(0  ≤ i ≤ 19): f = (b and c) xor ((not b) and d)          (alternative 2)
(0  ≤ i ≤ 19): f = (b and c) + ((not b) and d)            (alternative 3)
 
(40 ≤ i ≤ 59): f = (b and c) or (d and (b or c))          (alternative 1)
(40 ≤ i ≤ 59): f = (b and c) or (d and (b xor c))         (alternative 2)
(40 ≤ i ≤ 59): f = (b and c) + (d and (b xor c))          (alternative 3)
(40 ≤ i ≤ 59): f = (b and c) xor (b and d) xor (c and d)  (alternative 4)

SHA-256 (one of the SHA-2 versions) algorithm

Pseudocode for the SHA-256 algorithm follows. Pseudocode is a compact and informal high-level description of a Computer programming Algorithm that uses the structural conventions of some Programming language In Mathematics, modular arithmetic (sometimes called modulo arithmetic, or clock arithmetic) is a system of Arithmetic for Integers In combinatorial Mathematics, a circular shift is a Permutation of the entries in a Tuple where the last element becomes the first element Pseudocode is a compact and informal high-level description of a Computer programming Algorithm that uses the structural conventions of some Programming language Note the great increase in mixing between bits of the w[16. . 63] words compared to SHA-1.

Note: All variables are unsigned 32 bits and wrap modulo 232 when calculating

Initialize variables
(first 32 bits of the fractional parts of the square roots of the first 8 primes 2. . 19):
h0 := 0x6a09e667
h1 := 0xbb67ae85
h2 := 0x3c6ef372
h3 := 0xa54ff53a
h4 := 0x510e527f
h5 := 0x9b05688c
h6 := 0x1f83d9ab
h7 := 0x5be0cd19

Initialize table of round constants
(first 32 bits of the fractional parts of the cube roots of the first 64 primes 2. . 311):
k[0. . 63] :=
   0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
   0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
   0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
   0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
   0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
   0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
   0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
   0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2

Pre-processing:
append the bit '1' to the message
append k bits '0', where k is the minimum number >= 0 such that the resulting message
    length (in bits) is congruent to 448 (mod 512)
append length of message (before pre-processing), in bits, as 64-bit big-endian integer

Process the message in successive 512-bit chunks:
break message into 512-bit chunks
for each chunk
    break chunk into sixteen 32-bit big-endian words w[0. In Mathematics, modular arithmetic (sometimes called modulo arithmetic, or clock arithmetic) is a system of Arithmetic for Integers  . 15]

    Extend the sixteen 32-bit words into sixty-four 32-bit words:
    for i from 16 to 63
        s0 := (w[i-15] rightrotate 7) xor (w[i-15] rightrotate 18) xor (w[i-15] rightshift 3)
        s1 := (w[i-2] rightrotate 17) xor (w[i-2] rightrotate 19) xor (w[i-2] rightshift 10)
        w[i] := w[i-16] + s0 + w[i-7] + s1

    Initialize hash value for this chunk:
    a := h0
    b := h1
    c := h2
    d := h3
    e := h4
    f := h5
    g := h6
    h := h7

    Main loop:
    for i from 0 to 63
        s0 := (a rightrotate 2) xor (a rightrotate 13) xor (a rightrotate 22)
        maj := (a and b) xor (a and c) xor (b and c)
        t2 := s0 + maj
        s1 := (e rightrotate 6) xor (e rightrotate 11) xor (e rightrotate 25)
        ch := (e and f) xor ((not e) and g)
        t1 := h + s1 + ch + k[i] + w[i]

        h := g
        g := f
        f := e
        e := d + t1
        d := c
        c := b
        b := a
        a := t1 + t2

    Add this chunk's hash to result so far:
    h0 := h0 + a
    h1 := h1 + b 
    h2 := h2 + c
    h3 := h3 + d
    h4 := h4 + e
    h5 := h5 + f
    h6 := h6 + g 
    h7 := h7 + h

Produce the final hash value (big-endian):
digest = hash = h0 append h1 append h2 append h3 append h4 append h5 append h6 append h7

The ch and maj functions can be optimized the same way as described for SHA-1.

SHA-224 is identical to SHA-256, except that:

• the initial variable values h0 through h7 are different, and
• the output is constructed by omitting h7.

SHA-512 is identical in structure, but:

• all numbers are 64 bits long,
• there are 80 rounds instead of 64,
• the initial values and additive constants are extended to 64 bits, and
• the shift and rotate amounts used are different.

SHA-384 is identical to SHA-512, except that:

• the initial values h0 through h7 are different, and
• the output is constructed by omitting h6 and h7.

See also

• Digital timestamping
• Hash collision
• Hashcash
• RIPEMD-160 (Patent free)
• Secure Hash Standard
• Tiger
• WHIRLPOOL (Patent free)

References

External links

Online Hash Calculators

• Hash'em all! — free online text and file hashing with different algorithms
• http://www.johnmaguire.us/tools/hashcalc/index.php – Allows for the encoding of the zero-length string.

Standards: SHA-0, SHA-1, SHA-2, SHA-3. . .

• Specifications for a Secure Hash Standard (SHS) – Draft for proposed SHS standard (SHA-0)
• Secure Hash Standard (SHS) – Proposed SHS standard (SHA-0)
• CSRC Cryptographic Toolkit – Official NIST site for the Secure Hash Standard
  • FIPS 180-2: Secure Hash Standard (SHS) (PDF, 236 kB) – Current version of the Secure Hash Standard (SHA-1, SHA-224, SHA-256, SHA-384, and SHA-512), 1 August 2002, amended 25 February 2004
• NIST Cryptographic Hash Project SHA-3 competition

Cryptanalysis

• Interview with Yiqun Lisa Yin concerning the attack on SHA-1
• Lenstra's Summary of impact of the February 2005 cryptanalytic results
• Explanation of the successful attacks on SHA-1 (3 pages, 2006)
• Cryptography Research - Hash Collision Q&A

Implementations

• The OpenSSL Project – The widely used OpenSSL crypto library includes free, open-source implementations of SHA-1, SHA-224, SHA-256, SHA-384, and SHA-512
• Crypto++ Crypto++ Library is a free C++ class library of cryptographic schemes. OpenSSL is an Open source implementation of the SSL and TLS protocols Free software or software libre is Software that can be used studied and modified without restriction and which can be copied and redistributed in modified or unmodified Open source is a development methodology which offers practical accessibility to a product's source (goods and knowledge
• Bouncy Castle The Bouncy Castle Library is a free Java and C# class library that contains implementations of the SHA-1, SHA-224, SHA-256, SHA-384 and SHA-512 algorithms as well as other algorithms like Whirlpool, Tiger, RIPEMD, GOST-3411, MD2, MD4 and MD5. "WHIRLPOOL" redirects here This article is about the algorithm In Cryptography, Tiger is a Cryptographic hash function designed by Ross Anderson and Eli Biham in 1995 for efficiency on 64-bit RIPEMD-160 ( RACE Integrity Primitives Evaluation Message Digest) is a 160-bit Message digest algorithm (and Cryptographic hash function) developed Message Digest Algorithm 2 (MD2 is a Cryptographic hash function developed by Ronald Rivest in 1989. MD4 is a message digest Algorithm (the fourth in a series designed by Professor Ronald Rivest of MIT in 1990 In Cryptography, MD5 ( Message-Digest algorithm 5) is a widely used partially insecure Cryptographic hash function with a 128- Bit hash value
• File Hash for Windows with various algorithms including SHA