The Secure Hash Algorithms are a family of

cryptographic hash function A cryptographic hash function (CHF) is a hash algorithm (a map (mathematics), map of an arbitrary binary string to a binary string with a fixed size of n bits) that has special properties desirable for a cryptography, cryptographic application: ...

s published by the

National Institute of Standards and Technology The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into Outline of p ...

(NIST) as a

U.S. The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 states and a federal capital district, Washington, D.C. The 48 contiguous ...

Federal Information Processing Standard The Federal Information Processing Standards (FIPS) of the United States are a set of publicly announced standards that the National Institute of Standards and Technology (NIST) has developed for use in computer systems of non-military United Stat ...

(FIPS), including: * SHA-0: A

retronym A retronym is a newer name for something that differentiates it from something else that is newer, similar, or seen in everyday life; thus, avoiding confusion between the two. Etymology The term ''retronym'', a neologism composed of the combi ...

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 It was withdrawn shortly after publication due to an undisclosed "significant flaw" and replaced by the slightly revised version SHA-1.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 In cryptography, SHA-1 (Secure Hash Algorithm 1) is a hash function which takes an input and produces a 160-bit (20-byte) hash value known as a message digest – typically rendered as 40 hexadecimal digits. It was designed by the United States ...

: A 160-bit hash function which resembles the earlier

MD5 The MD5 message-digest algorithm is a widely used hash function producing a 128-bit hash value. MD5 was designed by Ronald Rivest in 1991 to replace an earlier hash function MD4, and was specified in 1992 as Request for Comments, RFC 1321. MD5 ...

algorithm. This was designed by the

National Security Agency The National Security Agency (NSA) is an intelligence agency of the United States Department of Defense, under the authority of the director of national intelligence (DNI). The NSA is responsible for global monitoring, collection, and proces ...

(NSA) to be part of the

Digital Signature Algorithm The Digital Signature Algorithm (DSA) is a Public-key cryptography, public-key cryptosystem and Federal Information Processing Standards, Federal Information Processing Standard for digital signatures, based on the mathematical concept of modular e ...

. Cryptographic weaknesses were discovered in SHA-1, and the standard was no longer approved for most cryptographic uses after 2010. *

SHA-2 SHA-2 (Secure Hash Algorithm 2) is a set of cryptographic hash functions designed by the United States National Security Agency (NSA) and first published in 2001. They are built using the Merkle–Damgård construction, from a one-way compression ...

: 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 SHA-3 (Secure Hash Algorithm 3) is the latest member of the Secure Hash Algorithm family of standards, released by NIST on August 5, 2015. Although part of the same series of standards, SHA-3 is internally different from the MD5-like stru ...

: A hash function formerly called ''

Keccak SHA-3 (Secure Hash Algorithm 3) is the latest member of the Secure Hash Algorithm family of standards, released by NIST on August 5, 2015. Although part of the same series of standards, SHA-3 is internally different from the MD5-like struct ...

'', 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.

Validation

All SHA-family algorithms, as FIPS-approved security functions, are subject to official validation by the CMVP (Cryptographic Module Validation Program), a joint program run by the American

(NIST) and the Canadian

Communications Security Establishment The Communications Security Establishment (CSE; , ''CST''), formerly (from 2008-2014) called the Communications Security Establishment Canada (CSEC), is the Government of Canada's national cryptologic agency. It is responsible for foreign signal ...

(CSE).

References

{{Cryptography hash Cryptography