4/20/01. EMTM 553. 2. Outline. How cryptography worksSecrete key cryptographyPublic key cryptographyDigital signatureMessage digestDistribution of public keysReal-world systems. 4/20/01. EMTM 553. 3. Cryptography: Basic Terminology. Plaintext (or cleartext)The message.Denoted by M or P.Encryption (encipher)Encoding of message.Denoted by E.CiphertextEncrypted message.Denoted by C.Decryption (decipher)decoding of ciphertextdenoted by D..