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MDC_Generate CCA Release 2.54
Chaining_Vector
The chaining_vector parameter is a pointer to an 18-byte string variable the
security server uses as a work area to hold segmented data between verb
invocations.
Note: When segmenting text, the application program must not change the
data in this string between verb calls to the MDC_Generate verb.
MDC
The MDC parameter is a pointer to a user-supplied MDC key or to a 16-byte
string variable containing the MDC value. This value can be the key that the
application program provides. This field is also used to hold the intermediate
MDC result when segmenting text.
Note: When segmenting text, the application program must not change the
data in this string between verb calls to the MDC_Generate verb.
Figure 4-2 (Page 2 of 2). MDC_Generate Rule_Array Keywords
Keyword Meaning
Algorithm Mode (one, optional)
PADMDC-2 Specifies two encipherments for each eight-byte block using
PADMDC procedures.
PADMDC-4 Specifies four encipherments for each eight-byte block using
PADMDC procedures.
MDC-2 Specifies two encipherments for each eight-byte block using
MDC procedures. This is the default.
Note: Use of the MDC-2 mode is not recommended.
MDC-4 Specifies four encipherments for each eight-byte block using
MDC procedures.
Note: Use of the MDC-4 mode is not recommended.
Required Commands
The MDC_Generate verb requires the Generate MDC command (offset X'008A')
to be enabled in the hardware.
Related Information
The MDC_Generate verb uses a default key when you specify ONLY or FIRST
keywords. If you want to use the MDC as a keyed-hash algorithm, place your key
into the MDC variable and ensure that the chaining_vector variable is set to null (18
bytes of X'00'). Then for a single segment of text, use the LAST keyword. For
multiple segments of text, begin with the MIDDLE keyword and then proceed to use
additional calls specifying MIDDLE as required and finally LAST; as with the default
key, you must not alter the value of the MDC or chaining_vector variables between
calls.
4-12 IBM 4758 CCA Basic Services, Release 2.54, February 2005