
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. 
