SHA-256

SHA-256 is a Cryptographic Hash Function|cryptographic hash function that produces a 256-bit (32-byte) digest from an input of arbitrary length, typically rendered as a 64-character hexadecimal string. It is the most widely deployed member of the SHA-2 family, which also includes SHA-224, SHA-384, and SHA-512. SHA-256 was designed by the U.S. National Security Agency and published by the National Institute of Standards and Technology (NIST) in 2001 as part of the draft FIPS PUB 180-2 standard, which became the Secure Hash Standard in August 2002. It was introduced to succeed SHA-1, whose 160-bit output had become too short to resist collision attacks. Internally, SHA-256 uses a Merkle-Damgård construction over 512-bit message blocks with 64 rounds of bitwise mixing, additions, and constants derived from the cube roots of the first 64 primes. Because no practical attack on SHA-256 is known, it serves as the workhorse hash for much of modern infrastructure. It secures TLS certificates and signed software updates, provides the proof-of-work puzzle in Bitcoin, anchors Merkle Tree structures in blockchains and Content-Addressable Storage systems including IPFS and the in-progress hash transition of Git (version control), and underlies HMAC-SHA-256 message authentication. The 256-bit output size is considered large enough to resist brute-force collision search well beyond the expected lifetime of current computing hardware.