Question

If a cryptanalyst only knows the encryption algorithm and ciphertext, then which type of attack can be performed by him?

• A. Known Plaintext Attack
• B. Ciphertext Only Attack
• C. Chosen Plaintext Attack
• D. Chosen Text Attack

Hint:

A Ciphertext Only Attack is the most difficult type of cryptanalytic attack since the attacker only has access to the encrypted message.

Answer 1

The Correct Option is B

Step 1: Understand Attack Types.
A Ciphertext Only Attack occurs when a cryptanalyst possesses solely the ciphertext, without its corresponding plaintext. This scenario involves knowledge of only the encryption algorithm and the ciphertext itself.

Step 2: Analyze Options.
- (A) Known Plaintext Attack: Requires both ciphertext and its corresponding plaintext.
- (B) Ciphertext Only Attack: Utilizes only the ciphertext, aligning with the described conditions.
- (C) Chosen Plaintext Attack: Involves the cryptanalyst selecting plaintext for encryption.
- (D) Chosen Text Attack: Similar to Chosen Plaintext Attack, but allows selection of both plaintext and ciphertext.

Step 3: Conclude.
The correct classification is (B) Ciphertext Only Attack.