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The Secure Hash Algorithm (SHA-1) creates:

The Secure Hash Algorithm (SHA-1) creates:

PrepAway - Latest Free Exam Questions & Answers

A.
a fixed length message digest from a fixed length input message.

B.
a variable length message digest from a variable length input message.

C.
a fixed length message digest from a variable length input message.

D.
a variable length message digest from a fixed length input message.

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.

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


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