Explanation/Reference:
Explanation:
SHA-1 was designed by NSA and published by NIST to be used with the Digital Signature Standard (DSS).
The Secure Hash Algorithm (SHA-1) computes a fixed length message digest from a variable length input message. This message digest is then processed by the DSA to either generate or verify the signature.
SHA-1 produces a message digest of 160 bits when any message less than 264 bits is used as an input.
SHA-1 has the following properties:
It is computationally infeasible to find a message that corresponds to a given message digest.

It is computationally infeasible to find two different messages that produce the same message digest.

For SHA-1, the length of the message is the number of bits in a message. Padding bits are added to the message to make the total length of the message, including padding, a multiple of 512.
Incorrect Answers:
A: SHA-1 creates a fixed length message digest from a variable length input message, not from a fixed length input message.
B: SHA-1 creates a fixed length message digest, not a variable length message digest.
D: SHA-1 creates a fixed length message digest, not a variable length message digest. The fixed length message digest is created from a variable length input message, not from a fixed length input message.
References:
Krutz, Ronald L. and Russel Dean Vines, The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, John Wiley & Sons, New York, 2001, p. 152