Exam CISSP Topic 5 Question 119 Discussion

Explanation/Reference:
Explanation:
Electronic Code Book (ECB) is the "native" mode of DES and is a block cipher. ECB is best suited for use with small amounts of data. It is usually applied to encrypt initialization vectors or encrypting keys. ECB is applied to 64-bit blocks of plaintext, and it produces corresponding 64-bit blocks of ciphertext.
Electronic Code Book (ECB) mode operates like a code book. A 64-bit data block is entered into the algorithm with a key, and a block of ciphertext is produced. For a given block of plaintext and a given key, the same block of ciphertext is always produced.
Incorrect Answers:
B: The DES Output Feedback Mode (OFB) is also a stream cipher that generates the ciphertext key by XORing the plaintext with a key stream. OFB mode is not the mode described in the question.
C: Counter Mode (CTR) is very similar to OFB mode, but instead of using a randomly unique IV value to generate the keystream values, this mode uses an IV counter that increments for each plaintext block that needs to be encrypted. CTR mode is not the mode described in the question.
D: The Cipher Feedback Mode (CFB) of DES is a stream cipher where the ciphertext is used as feedback into the key generation source to develop the next key stream. CFB mode is not the mode described in the question.
References:
Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, p. 803 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. 143