In which of the following cryptographic attacking techniques does an attacker obtain encrypted messages that have been encrypted using the same encryption algorithm?

Question

Options

• AChosen plaintext attack
• BCiphertext only attack
• CChosen ciphertext attack
• DKnown plaintext attack

• A
  4% (1)
• B
  93% (26)
• D
  4% (1)

Explanation

Ciphertext Only Attack (B) is correct because in this scenario, the attacker's only resource is a collection of ciphertexts-all encrypted with the same algorithm-and must attempt to deduce the key or plaintext without any other information. The question's phrasing "obtain encrypted messages" with nothing else given is the defining characteristic of this attack.

Why the distractors are wrong:

• A (Chosen Plaintext): The attacker actively selects specific plaintexts and obtains their corresponding ciphertexts-far more attacker control than just passively collecting ciphertexts.
• C (Chosen Ciphertext): The attacker selects specific ciphertexts and obtains their decryptions-again, an active attack with more power than simply observing ciphertexts.
• D (Known Plaintext): The attacker already possesses matching plaintext-ciphertext pairs, giving them more information than a pure ciphertext-only scenario.

Memory tip: Think of the attacks on a scale of attacker knowledge - Ciphertext Only = least info (just encrypted output), Known Plaintext = also has some plaintext, Chosen Plaintext/Ciphertext = attacker controls the inputs. If the question describes an attacker with nothing but ciphertexts, it's always Ciphertext Only.

No community discussion yet for this question.