Systems Security Certified Practitioner – SSCP – Question0741

What is the effective key size of DES?

A.
56 bits
B. 64 bits
C. 128 bits
D. 1024 bits

Correct Answer: A

Explanation:

Data Encryption Standard (DES) is a symmetric key algorithm. Originally developed by IBM, under project name Lucifer, this 128-bit algorithm was accepted by the NIST in 1974, but the total key size was reduced to 64 bits, 56 of which make up the effective key, plus and extra 8 bits for parity. It somehow became a national cryptographic standard in 1977, and an American National Standard Institute (ANSI) standard in 1978. DES was later replaced by the Advanced Encryption Standard (AES) by the NIST.
Source: HARRIS, Shon, All-In-One CISSP Certification Exam Guide, McGraw-Hill/Osborne, 2002, chapter 8: Cryptography (page 525).