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CCA Release 2.54
MDC-2 Calculation
The MDC-2 calculation consists of the following procedure:
MDC-2 (n, text, KEY1, KEY2, MDC);
For i := 1,2,...,n do
Call MDC-1(KEY1, KEY2, T8<i>, T8<i>, OUT1, OUT2)
Set KEY1 := OUT1
Set KEY2 := OUT2
End do
Set output MDC := (KEY1 || KEY2).
End procedure
MDC-4 Calculation
The MDC-4 calculation consists of the following procedure:
MDC-4 (n, text, KEY1, KEY2, MDC);
For i := 1,2,...n do
Call MDC-1(KEY1,KEY2,T8<i>,T8<i>,OUT1,OUT2)
Set KEY1int := OUT1
Set KEY2int := OUT2
Call MDC-1(KEY1int,KEY2int,KEY2,KEY1,OUT1,OUT2)
Set KEY1 := OUT1
Set KEY2 := OUT2
End do
Set output MDC := (KEY1 || KEY2)
End procedure
Ciphering Methods
The Data Encryption Standard (DES) algorithm defines operations on eight-byte
data strings. The DES algorithm is used in many different processes within CCA:
Encrypting general data
Triple-encrypting PIN blocks
Triple-encrypting CCA DES keys
Triple-encrypting RSA private keys...with several processes
Deriving keys, hashing data, generating CVV values, etc.
The Encipher and Decipher describe how you can request encryption of
application data. See “General Data Encryption Processes” on page D-6 for a
description of the two supported standardized processes.
In CCA, PIN blocks are encrypted with double-length keys. The PIN block is
encrypted with the left-half key, which result is decrypted with the right-half key
and this result is encrypted with the left-half key.
“CCA DES Key Encryption and Decryption Processes” on page C-12 describes
how CCA DES keys are enciphered.
“Triple-DES Ciphering Algorithms” on page D-10 describes how CCA DES keys
are enciphered.
Appendix D. Algorithms and Processes D-5