Certified Information Systems Security Professional (CISSP) — Question 476

Using the cipher text and resultant cleartext message to derive the monoalphabetic cipher key is an example of which method of cryptanalytic attack?

Answer options

• A. Known-plaintext attack
• B. Ciphertext-only attack
• C. Frequency analysis
• D. Probable-plaintext attack

Correct answer: A

Explanation

The correct answer is A, as a known-plaintext attack specifically utilizes both the cipher text and the corresponding plain text to deduce the cipher key. The other options do not involve the use of known cleartext alongside cipher text in their methods, making them incorrect in this context.