Produces a 160-bit representation of the message, called the message digest, when a message with a bit length less than 2 to 64th power is input. The message digest is used during the generation of a signature for the message. The message digest is computed during the generation of a signature for the message. The SHA-1 is also used to compute a message digest for the received version of the message during the process of verifying the signature. Any change to the message in transit will, with a very high probability, result in a different messages digest, and the signature will fail to verify. The Secure Hash Algorithm (SHA-1) described in this standard is required for use with the Digital Signature Algorithm and may be used whenever a secure hash algorithm is required.