Dictionary of Information Security

Dictionary of Information Security 35

form “CHRISTMA EXEC” is used almost univer-

sally.The more correct form is “CHRISTMA exec,”

since REXX scripts were referred to as “execs” to

distinguish them from the earlier EXEC language in

IBM mainframes.)

CIAC see Computer Incident Advisory Capability

cipher cryptographic algorithm for encryption and decryption

cipher block chaining (CBC) block cipher mode that

enhances electronic codebook mode by chaining

together blocks of ciphertext it produces.This mode

operates by combining (exclusive OR-ing) the algo-

rithm’s ciphertext output block with the next plain-

text block to form the next input block for the

algorithm.

cipher feedback (CFB) block cipher mode that enhances

electronic codebook mode by chaining together ...