SHA (Secure Hash Algorithm)

SHA (Secure Hash Algorithm)

SHA-1 (Secure Hash Algorithm) is a hash function made by the NSA (National Security Agency) and publicated by the NIST (National Institute of Standards and Technology) as information processing standard. Since 2005, SHA-1 has not been considered secure against well-funded opponents. In 2011, NIST formally deprecated use of SHA-1 and disallowed


SHA-0 is 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 It was withdrawn shortly after publication due to an undisclosed “significant flaw” and replaced by the slightly revised version SHA-1.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 is a 160-bit hash function which resembles the earlier MD5 algorithm. This was designed by the 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 is 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-byte words where SHA-512 uses 64-byte 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 is a hash function formerly called 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.