Explanation/Reference:
Explanation:
Data Encryption Standard (DES) has had a long and rich history within the computer community. NIST invited vendors to submit data encryption algorithms to be used as a cryptographic standard. IBM had already been developing encryption algorithms to protect financial transactions. In 1974, IBM's 128-bit algorithm, named Lucifer, was submitted and accepted. The NSA modified this algorithm to use a key size of 64 bits (with 8 bits used for parity, resulting in an effective key length of 56 bits) instead of the original
128 bits, and named it the Data Encryption Algorithm (DEA).
NOTE DEA is the algorithm that fulfills DES, which is really just a standard. So DES is the standard and DEA is the algorithm, but in the industry we usually just refer to it as DES. The CISSP exam may refer to the algorithm by either name, so remember both.
Incorrect Answers:
A: The Data Encryption Standard algorithm has an effective key length of 56 bits, not 168 bits.
B: The Data Encryption Standard algorithm has an effective key length of 56 bits, not 128 bits.
D: The Data Encryption Standard algorithm has an effective key length of 56 bits, not 64 bits.
References:
Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, p. 800