Once encrypted, the message is called ciphertext. The ATM machine sends the ciphertext of your PIN number and your request for cash to your bank. Turning ciphertext back into plaintext is called decryption. The bank decrypts the message containing your PIN number. Encryption and decryption are part of the art and science of keeping messages secure, of creating secret writing, which is called cryptography.
Cryptography is practiced by cryptographers.
The branch of mathematics that embodies cryptography and cryptanalysis is called cryptology. For many years the discipline of cryptography was conducted behind the closed doors of secretive governmental agencies. But the new popularity of the Internet is bringing cryptography into the public's awareness in new ways. The strength of an encryption system can be expressed in five basic principles. In cryptography, since there is no place for sealing wax and signet rings, identification rests on the notion that some part of the encoded information must positively identify its source.