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Definition: SHA


(Secure Hash Algorithm) A family of popular cryptographic hash algorithms used to create digital signatures that verify the integrity of data. In 1993, the 160-bit SHA was developed by the National Institute of Standards & Technology (NIST).

SHA-1, SHA-2 and SHA-3
SHA-1 was the first SHA revision in 1994. SHA-1 is similar to the MD4 and MD5 algorithms developed by Rivest, but is slightly slower and more secure (see MD5). Released in 2001, SHA-2 was a stronger algorithm. SHA-3 came out in 2015 and supports the same hash lengths as SHA-2 but uses a different method based on the Keccak algorithm. SHA-3 was the result of a NIST competition for a new hash standard that began in 2006 and ended in 2012.

SHA-256 and SHA-512
SHA-256 and SHA-512 are SHA-2 algorithms using hash lengths of 256 and 512 bits respectively, and SHA-224 and SHA-384 are truncated versions. SHA-256 is the hash algorithm used in the Bitcoin blockchain (see HASH160). See cryptographic hash function and digital signature.