Explanation/Reference:
Explanation:
A message digest should be calculated using all of the original file's data regardless of whether the original data is more or less than 128 bytes.
The output of a hash function is called a message digest. The message digest is uniquely derived from the input file and, if the hash algorithm is strong, the message digest has the following characteristics:
1. The hash function is considered one-way because the original file cannot be created from the message digest.
2. Two files should not have the same message digest.
3. Given a file and its corresponding message digest, it should not be feasible to find another file with the same message digest.
4. The message digest should be calculated using all of the original file's data.
Incorrect Answers:
A: It is true that the original file cannot be created from the message digest.
B: It is true that two different files should not have the same message digest.
D: It is true that message digests are usually of fixed size.
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. 151-152