IBM Computer Hardware 2 User Manual download pdf (Page 444)

100

101

CCA Release 2.54

When the keywords PADMDC-2 and PADMDC-4 are used, the supplied text is

always padded as follows:

 If the supplied text is less than 16 bytes in length, pad bytes are appended to

make the text length equal to 16 bytes.

 If the supplied text is at least 16 bytes in length, pad bytes are appended to

make the text length equal to the next-higher multiple of eight bytes, pad bytes

are always added.

 All appended pad bytes, other than the last pad byte, are set to X'FF'.

 The last pad byte is set to a binary value equal to the count of all appended

pad bytes (X'01' to X'10').

Use the resulting pad text in the following procedures. The MDC_Generate verb

uses these MDC calculation methods. See page 4-10 for more information about

the MDC_Generate verb.

Notation Used in Calculations

The MDC calculations use the following notations:

eK(X) Denotes DES encryption of plaintext X using key K

|| Denotes the concatenation operation

XOR Denotes the exclusive-OR operation

:= Denotes the assignment operation

T8<1> Denotes the first eight-byte block of text

T8<2> Denotes the second eight-byte block of text, and so on

KD1, KD2, IN1, IN2, OUT1, OUT2

Denote 64-bit quantities

MDC-1 Calculation

The MDC-1 calculation, which is used in the MDC-2 and MDC-4 calculations,

consists of the following procedure:

MDC-1 (KD1, KD2, IN1, IN2, OUT1, OUT2);

Set KD1mod := set bit 1 and bit 2 of KD1 to "1" and "" respectively.

Set KD2mod := set bit 1 and bit 2 of KD2 to "" and "1" respectively.

Set F1 := IN1 XOR eKD1mod(IN1)

Set F2 := IN2 XOR eKD2mod(IN2)

Set OUT1 := (bits ..31 of F1) || (bits 32..63 of F2)

Set OUT2 := (bits ..31 of F2) || (bits 32..63 of F1)

End procedure

D-4 IBM 4758 CCA Basic Services, Release 2.54, February 2005

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