ciphertext-only attack

ciphertext-only attack (plural ciphertext-only attacks)

1. (cryptography) An attack on a cryptosystem that relies only on the attacker's knowledge of some ciphertexts encrypted with that system and key. Less powerful than a known-plaintext attack.

• known-ciphertext attack
• COA (initialism)

• known-plaintext attack, chosen-plaintext attack, chosen-ciphertext attack