Meaning – The term initial chaining value, refers to an 8-byte pseudo-random number used to verify that both ends of a session with cryptography have the same session cryptography key. The initial chaining value is also used as input to the Data Encryption Standard (DES) algorithm to encipher or decipher data in a session with cryptography.
The cipher block chaining (CBC) mode uses an initial chaining value (ICV) in its processing. The first 8 bytes of ciphertext is deciphered and then the ICV is exclusive ORed with the resulting 8 bytes of data to form the first 8-byte block of plaintext. Thereafter, the 8-byte block of ciphertext is deciphered and exclusive ORed with the previous 8-byte block of ciphertext until all the ciphertext is deciphered.
Example of usage – “A different ICV may be passed on each call to the decipher callable service. However, the same ICV that was used in the corresponding encipher callable service must be passed”