Certified Ethical Hacker (CEH v11) — Question 35

What is the known plaintext attack used against DES which gives the result that encrypting plaintext with one DES key followed by encrypting it with a second
DES key is no more secure than using a single key?

Answer options

• A. Man-in-the-middle attack
• B. Meet-in-the-middle attack
• C. Replay attack
• D. Traffic analysis attack

Correct answer: B

Explanation

The correct answer is B, Meet-in-the-middle attack, which illustrates that the security of encrypting with two DES keys is equivalent to using one key due to the vulnerabilities in the algorithm. The other options, such as Man-in-the-middle attack, Replay attack, and Traffic analysis attack, refer to different types of security threats and do not relate to the specific issue with DES encryption.