SHA-2

Also known as SHA-512/224, SHA512/256, SHA 2, SHA-224, SHA512/224, SHA256, SHA-512/256, SHA-384

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 function itself built using the Davies–Meyer structure from a specialized block cipher.

Key facts

Cryptographic hash function.name: SHA-2
Cryptographic hash function.image: SHA-2.svg
Cryptographic hash function.designers: National Security Agency
Cryptographic hash function.series: (SHA-0), SHA-1, SHA-2, SHA-3
Cryptographic hash function.certification: FIPS PUB 180-4, CRYPTREC, NESSIE
Cryptographic hash function.digest size: 224, 256, 384, or 512 bits
Cryptographic hash function.structure: Merkle–Damgård construction with Davies–Meyer compression function
Cryptographic hash function.rounds: 64 or 80
Cryptographic hash function.cryptanalysis: A 2011 attack breaks preimage resistance for 57 out of 80 rounds of SHA-512, and 52 out of 64 rounds for SHA-256. Pseudo-collision attack against up to 46 rounds of SHA-256.

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inception: 2002-00-00

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~26 min read

Article

12 sections

Contents

Hash standard
Applications
Cryptanalysis and validation
Official validation
Test vectors
Pseudocode
Comparison of SHA functions
Implementations
See also
References
Further reading
External links

SHA-2 includes significant changes from its predecessor, SHA-1. The SHA-2 family consists of six hash functions with digests (hash values) that are 224, 256, 384 or 512 bits: SHA-224, SHA-256, SHA-384, SHA-512, SHA-512/224, SHA-512/256. SHA-256 and SHA-512 are hash functions whose digests are eight 32-bit 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 truncated versions of SHA-256 and SHA-512 respectively, computed with different initial values. SHA-512/224 and SHA-512/256 are also truncated versions of SHA-512, but the initial values are generated using the method described in Federal Information Processing Standards (FIPS) PUB 180-4.