Known-plaintext attack

The known-plaintext attack is a cryptanalytic attack in which the attacker has samples of both the plaintext and its encrypted version (ciphertext) and is at liberty to make use of them to reveal further secret information; typically this is the secret key.

At Bletchley Park in World War II, strenuous efforts were made to use, and even force the Germans to produce messages with, known plaintext. The known plaintexts were called "cribs", and schemes to force the Germans to produce them were called "gardening".

See also

• Chosen plaintext attack
• Ciphertext only attack