Chosen-ciphertext attack

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

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