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SHA-2 is a family of cryptographic hash functions , the de facto standard for current developments. It was originally published by NIST in 2001. It is based on a construction. It is replacing the older SHA-1 hash function and the even older MD5 .

The family comprises 6 functions with different output lengths.

  • SHA-256 and SHA-512 are the most commonly used hash functions. Their internal state and output size are both 256 for SHA-256 and both 512 for SHA-512. The algorithms are similar, but SHA-256 is expressed in terms of computations on 32-bit words while SHA-512 uses 64-bit words. SHA-512 has more rounds (80) than SHA-256 (64).
  • SHA-224 and SHA-384 are very similar to SHA-256 and SHA-512 respectively, but with output truncated to a smaller size, and different constants.
  • SHA-512/224 and SHA-512/256 (added in 2012) are truncated versions of SHA-512, also with different constants.

In 2012, NIST selected proposal for a SHA-3 algorithm. Although SHA-3 was initially intended as a replacement for SHA-2, it is now planned that SHA-2 and SHA-3 will coexist.

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