Cryptology isa science concerned with data communications and storage in secure and usually secret form. It encompasses both cryptography and cryptanalysis.
Cryptography originally was the study of the principles and techniques by which information could be concealed in ciphers (secret keys) and later revealed by users employing the secret key, but now encompasses the whole area of key-controlled transformations of information into forms that are either impossible or computationally infeasible for unauthorized persons to duplicate or undo.
Cryptanalysis is the science of recovering or forging cryptographically secured information without knowledge of the key.
(From Encyclopedia Britannica)