The Message Authentication Code (MAC) is a widely used technique for
performing message authentication. HMAC (short for "keyed-Hashing for
Message Authentication"), a variation on the MAC algorithm, has emerged
as an Internet standard for a variety of applications.
In cryptography, SHA-1 (Secure Hash Algorithm 1) is a cryptographic hash
function designed by the United States National Security Agency and is a
U.S. Federal Information Processing Standard published by the United
State NIST. SHA1 is used in many places to generate a unique Hash value
representing a string or file. It is widely used in place of MD4 and MD5
a more secure hash value. While not as secure as SHA256, it is still used
many places for data integrity, version control, and other features that
need an unique one-way signatures.