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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-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. [3] [4] 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.
SHA-384 and the lesser-known SHA-512/224 and SHA-512/256 are all variants of SHA-512. SHA-512 is more secure than SHA-256 and is commonly faster than SHA-256 on 64-bit machines such as AMD64. The output size in bits is given by the extension to the "SHA" name, so SHA-224 has an output size of 224 bits (28 bytes); SHA-256, 32 bytes; SHA-384, 48 ...
256 256 512 64 [note 3] 32 10 BLAKE3: Unlimited [note 4] 256 [note 5] 512 64 32 7 GOST: 256 256 256 256 32 32 HAVAL: 256/224/192/160/128 256 1024 64 32 3/4/5 MD2: 128 384 128 – 32 18 MD4: 128 128 512 64 32 3 MD5: 128 128 512 64 32 64 PANAMA: 256 8736 256 – 32 – RadioGatún: Unlimited [note 6] 58 words 19 words [note 7] – 1–64 [note 8 ...
SHA-3 instances are drop-in replacements for SHA-2, intended to have identical security properties. SHAKE will generate as many bits from its sponge as requested, thus being extendable-output functions (XOFs). For example, SHAKE128(M, 256) can be used as a hash function with a 256 character bitstream with 128-bit security strength.
For example, SHA-256 operates on 512-bit blocks. The size of the output of HMAC is the same as that of the underlying hash function (e.g., 256 and 512 bits in the case of SHA-256 and SHA3-512, respectively), although it can be truncated if desired. HMAC does not encrypt the message.
However, most common implementations use a fixed bit-size (generally 64 or 128 bits in modern algorithms) at a fixed position at the end of the last block for inserting the message length value (see SHA-1 pseudocode). Further improvement can be made by inserting the length value in the last block if there is enough space.
As of October 2012, CNSSP-15 [4] stated that the 256-bit elliptic curve (specified in FIPS 186-2), SHA-256, and AES with 128-bit keys are sufficient for protecting classified information up to the Secret level, while the 384-bit elliptic curve (specified in FIPS 186-2), SHA-384, and AES with 256-bit keys are necessary for the protection of Top ...