adaptive-chosen-ciphertext - A version of the chosen-ciphertext attack where the cryptanalyst can choose ciphertexts dynamically. A Cryptanalyst can mount an attack of this type in a scenario in which he or she has free use of a piece of decryption hardware, but is unable to extract the decryption key from it.

adaptive-chosen-plaintext - A special case of the chosen-plaintext attack in which the cryptanalyst is able to choose plaintexts dynamically, and alter his or her choices base on the results of previous encryptions.

adversary - Commonly used to refer to the opponent, the enemy, or any other mischievous person that desires to compromise one's security.

AES - The Advanced Encryption Standard that will replace DES (The Data Encryption Standard) around the turn of the century.

algebraic attack - A method of cryptanalytic attack used against block ciphers that exhibit a significant amount of mathematical structure.

algorithm - A series of steps used to complete a task.

Alice - The name traditionally used for the first user of cryptography in a system: Bob's friend.

ANSI - American National Standards Institute.

API - Application Programming Interface.

attack - Either a successful or unsuccessful attempt at breaking part or all of a cryptosystem. See algebraic attack, birthday attack, brute force attack, chosen ciphertext attack, chosen plaintext attack, differential cryptanalysis, known plaintext attack, linear cryptanalysis, middleperson attack.

authentication - The action of verifying information such as identity, ownership or authorization.

biometrics - The science of using biological properties to identify individuals; for example, fingerprints, retina scan and voice recognition.

birthday attack - A brute-force attack used to find collisions. It gets its name from the surprising result that the probability of two or more people in a group of 23 sharing the same birthday is greater than 1/2.

bit - A binary digit, either 1 or 0.

blind signature scheme - Allows one party to have a second party sign a message without revealing any (or very little) information about the message to the second party.

block - A sequence of bits of fixed length; longer sequences of bits can be broken down into blocks.

block cipher - A symmetric cipher which encrypts a message by breaking it down into blocks and encrypting each block.

block cipher based MAC - MAC that is preformed by using a block cipher as a keyed compression function.

Bob - The name traditionally used for the second user of cryptography in a system; Alice's friend.

boolean expression - A mathematical expression in which all variables involved are either 0 or 1; it evaluates to either 0 or 1.