SHA-1 (Secure Hash Algorithm 1) is a cryptographic hash function designed to take any input and produce a fixed-size, 160-bit (20-byte) hash value, commonly referred to as a message digest. This digest is typically displayed as a 40-character hexadecimal string. SHA-1 was developed by the U.S. National Security Agency (NSA) and published as a federal standard by the National Institute of Standards and Technology (NIST).
SHA-1 processes data of any size and outputs a unique, fixed-length hash. It is deterministic: the same input always produces the same output. The hash is designed to be irreversible, meaning you cannot reconstruct the original data from the hash. It uses the Merkle–Damgård construction, a common structure for cryptographic hash functions.