What is a SHA1-hash?

The Secure Hash Algorithm (SHA1) is a widely used cryptographic hash function, that generates a 160-bit (20-byte) hash from any input value. This is used to calculate a unique check value for any digital data (messages) of no more than 2⁶⁴ -1 bit (≈ 2 Exbibyte) length and is the basis for creating a digital signature. SHA1 was developed by the National Institute of Standards and Technology (NIST) in collaboration with the National Security Agency (NSA) in 1993. SHA-1 (originally SHA-0) is similar in construction to the algorithm of Ronald L. Rivest, who developed Message-Digest Algorithm 5 (MD5) in 1991.