SHA is a Cryptographic Language. SHA stands for Secure Hash Algorithm. United States National Security Agency designed this cryptographic hash function. It is a United States Federal Information Processing Standards which is published by the United States National Institute of Standards and Technology. (USNIST). The first SHA or SHA-1 produces standard 160 bit or 20 byte hash value. This is also known as message digest.
SHA-256 is also a Cryptographic Hash Algorithm. A message digest or a cryptographic hash is a signature to set off a data file or text. As the digit suggests, SHA-256 generates a 256 bit or 32 byte signature for a text. This SHA-256 is almost unique.
A hashing algorithm is a mathematical function. It condenses data to a fixed size. Hashes are useful for computers to identify, compare or do chores against files or data strings. Hashes are more convenient for the computers to compute than original files.
SHA-256 file compression function functions on 512 bit message block and a 256 bit intermediate hash value. SHA-256 is a256 bit block cipher algorithm. It encrypts the intermediate hash value.
It uses message block as Key. SHA-256 has two distinct functions:
One- SHA-256 file compression functions.
Two- SHA-256 message schedule.