Privacy transformations, both reversible and irreversible, are techniques for increasing data security and privacy in computerized databank systems. Irreversible transformations, such as data aggregation, are used primarily in statistical databanks. Reversible privacy transformations, often referred to as cryptographic transformations, are used in communication systems and, more recently, for protection of data and programs in computerized information systems and databanks against unauthorized access. This paper briefly discusses irreversible transformations and, then, focuses on the reversible transformations and their use for computer security. Various transformation classes are examined, their suitability and effectiveness discussed, and various implementation considerations explored. 50 pp. Ref.