CryptanaJ ysts not only have access to the ciphel1ext and associated pIaintext for several messages, but they also choose the encrypted pIaintext. This is more powerful than a known-paintext attack, because cryptanaysts can choose specific plaintext blocks to encrypt, ones that might yield more information about the key. Thejob is to deduce the key (or keys) used to encrypt the rnessages or an algorithm to decrypt any new messages encrypted with the same key.