
Cryptography  The mathematical process that first alters information so it appears meaningless. Cryptography then uses an information "key" which reverses the effects of the altercation process and restores the information to something comprehensible. There are two kinds of cryptography: symmetric, in which the key that locks the information is also the key that unlocks it; and asymmetric, in which the key that locks the information is different from the key that unlocks it. See the Interactive Television Institute. 
