| 1. | the science or study of the techniques of secret writing, esp. code and cipher systems, methods, and the like. Compare cryptanalysis (def. 2). |
| 2. | the procedures, processes, methods, etc., of making and using secret writing, as codes or ciphers. |
| 3. | anything written in a secret code, cipher, or the like. |
The science of coding and decoding messages so as to keep these messages secure. Coding (see encryption) takes place using a key that ideally is known only by the sender and intended recipient of the message.
Note: Historically used in warfare, cryptography is now used routinely in computer networks. This often pits the desire of individuals and businesses to keep Internet information private against the need of government to investigate crime and terrorism.