IBM Computer Hardware 2 User Manual download pdf (Page 445)

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101

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

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