Chosen-ciphertext attack

A chosen-ciphertext attack (CCA) is an attack model for cryptanalysis in which the cryptanalyst can gather information by obtaining the decryptions of chosen ciphertexts. From those pieces of information, the adversary can attempt to recover the secret key used for decryption.

For formal definitions of security against chosen-ciphertext attacks, see, for example, Michael Luby and Mihir Bellare et al.