SHA1
Secure Hashing Algorithm 1

SHA1 is one of several cryptographic hashing functions developed by the NSA (National Security Agency). Hashing functions compute a fixed-length digital representation (known as a message digest) of an input data sequence (the message) of any length. They are termed secure when it is computationally infeasible to find a message that corresponds to a given message digest or find two different messages that produce the same message digest. Also, any change to a message should, with a very high probability, result in a different message digest. It should be noted that SHA-1 is considered to be insecure by some industry experts, although SHA-2 and SHA-3 are still potential options.