Hashing
SHA (Secured Hash Algorithm)
Secured Hash Algorithm is a set of cryptographic hash functions designed by the United States National Security Agency (NSA) and first published in 2001.SHA-2 includes significant changes from its predecessor, SHA-1.
The SHA-2 family consists of six hash functions with digests (hash values) that are 224, 256, 384 or 512 bits: SHA-224, SHA-256, SHA-384, SHA-512, SHA-512/224, SHA-512/256. SHA-256 and SHA-512 are novel hash functions computed with 32-bit and 64-bit words, respectively.
Hash standard
With the publication of FIPS PUB 180–2, NIST added three additional hash functions in the SHA family. The algorithms are collectively known as SHA-2, named after their digest lengths (in bits): SHA-256, SHA-384, and SHA-512.
What’s Hashing ?
In cryptography, a hash function is a mathematical algorithm that maps data of any size to a bit string of a fixed size. We can refer to the function input as message or simply as input. The fixed-size string function output is known as the hash or the message digest.
It’s easy and practical to compute the hash, but “difficult or impossible to re-generate the original input if only the hash value is known.”
It’s difficult to create an initial input that would match a specific desired output.
Commonly used hashing algorithms include Message Digest (MDx) algorithms, such as MD5, and Secure Hash Algorithms (SHA), such as SHA-1 and the SHA-2 family that includes the widely used SHA-256 algorithm.
In bitcoin, integrity and block-chaining use the SHA-256 algorithm as the underlying cryptographic hash function.
