In which of the following cryptographic attacking techniques does the attacker pick up the information to be encrypted and take a copy of it with the encrypted data?

Question

Options

• AChosen ciphertext attack
• BKnown plaintext attack
• CChosen plaintext attack
• DCiphertext only attack

• A
  3% (1)
• B
  3% (1)
• C
  94% (34)

Explanation

Chosen plaintext attack (C) is correct because the attacker actively selects specific plaintext messages, submits them for encryption, and retains both the original plaintext and the resulting ciphertext. This gives the attacker curated input-output pairs to analyze the encryption scheme's behavior, potentially revealing the key or algorithm weaknesses.

Why the distractors are wrong:

• A (Chosen ciphertext): The attacker chooses ciphertexts and obtains their decryptions - the reverse scenario.
• B (Known plaintext): The attacker passively has some plaintext-ciphertext pairs but did not choose which plaintexts to encrypt.
• D (Ciphertext only): The attacker has only ciphertext with no access to any plaintext - the most limited attack scenario.

Memory tip: Think of it as "Choose → Encrypt → Copy both." If the attacker is doing the choosing and ends up with both versions, that's Chosen Plaintext. The word "chosen" always refers to whatever the attacker picks before the operation (plaintext = before encryption; ciphertext = before decryption).

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