A cryptanalysts chore is to break an encryption. That is the cryptanalyst attempts to m, deduce the original meaning of a ciphertext message. Better yet, he or she hopes to determine which decrypting algorithm matches the encrypting algorithm, so that other message encoded in the same way can be broken. Thus a cryptanalyst can do any or all of six different things-

Attempt to break a single message

Attempt to recognize patterns in encrypted messages, to be able to break subsequent ones by applying a straightforward decryption algorithm

Attempt to infer some meaning without even breaking the encryption, such as noticing an unusual frequency of communication or determining something by whether the communication was short or long.

Attempt to deduce the key in order to break subsequent message easily

Attempt to find weaknesses in the implementation or environment of use of encryption.