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{{short description|Family of cryptographic hash functions}}
The '''Secure Hash Algorithms''' are a family of [[Cryptographic hash function|cryptographic hash function]]s published by the [[Organization:National Institute of Standards and Technology|National Institute of Standards and Technology]] (NIST) as a {{wipe|United States of America}} Federal Information Processing Standard (FIPS), including:

*'''SHA-0''': A retronym applied to the original version of the 160-bit hash function published in 1993 under the name "SHA". It was withdrawn shortly after publication due to an undisclosed "significant flaw" and replaced by the slightly revised version SHA-1.
*'''[[SHA-1]]''': A 160-bit hash function which resembles the earlier [[MD5]] algorithm. This was designed by the [[Organization:National Security Agency|National Security Agency]] (NSA) to be part of the [[Digital Signature Algorithm]]. Cryptographic weaknesses were discovered in SHA-1, and the standard was no longer approved for most cryptographic uses after 2010.
*'''[[SHA-2]]''': A family of two similar hash functions, with different block sizes, known as ''SHA-256'' and ''SHA-512''. They differ in the word size; SHA-256 uses 32-bit words where SHA-512 uses 64-bit words. There are also truncated versions of each standard, known as ''SHA-224'', ''SHA-384'', ''SHA-512/224'' and ''SHA-512/256''. These were also designed by the NSA.
*'''[[SHA-3]]''': A hash function formerly called ''[[SHA-3|Keccak]]'', chosen in 2012 after a public competition among non-NSA designers. It supports the same hash lengths as SHA-2, and its internal structure differs significantly from the rest of the SHA family.

The corresponding standards are FIPS PUB 180 (original SHA), FIPS PUB 180-1 (SHA-1), FIPS PUB 180-2 (SHA-1, SHA-256, SHA-384, and SHA-512). NIST has updated Draft FIPS Publication 202, SHA-3 Standard separate from the Secure Hash Standard (SHS).

==Comparison of SHA functions==
In the table below, ''internal state'' means the "internal hash sum" after each compression of a data block.
{{Further|Merkle–Damgård construction}}

{{Comparison of SHA functions}}

== Validation ==
{{Main article|Cryptographic Module Validation Program}}

All SHA-family  algorithms, as FIPS-approved security functions, are subject to official validation by the [[Cryptographic Module Validation Program|CMVP]] (Cryptographic Module Validation Program), a joint program  run by the  American [[Organization:National Institute of Standards and Technology|National Institute of Standards and Technology]] (NIST) and the Canadian [[Organization:Communications Security Establishment|Communications Security Establishment]] (CSE).

== References ==
{{reflist}}

{{Cryptography hash}}

[[Category:Cryptography]]

{{Sourceattribution|Secure Hash Algorithms}}