Transaction Response with Auth Para from Card Issuer

Command:

Generate a MAC on a response message to a terminal and the new Key Register value encrypted under the LMK. Also, generate new MAC residue under the LMK.

Notes:

The command is used to respond to requests from terminals at the acquirer Host.

 

Field

Length & Type

Details

COMMAND MESSAGE

Message header

m A

(Subsequently returned to the Host unchanged).

Command code

2 A

Value RO.

Terminal key register

16 H

The terminal key register encrypted under LMK pair 14-15.

Fields A & B

16 H

The A & B fields as defined in the Racal Security Scheme.

ZPK or flag

16H or
1A+32H or 1A+48H or A

The ZPK under which Auth Para is encrypted, or the character L if Auth Para is encrypted under the LMK.

Auth Para

16 H

The authorization parameter either encrypted under ZPK or under LMK pair 14-15 (as indicated in the previous field).

MAC residue

8 H

The MAC residue from the request message processing; encrypted under LMK 10.

Message length

2 H

Value X’00 to X’A0 (decimal 160) indicating the length of the next field.  This field should be set to X'00 and the next field omitted if extended length messages required.

Message text

n A

The response message on which the response MAC should be calculated. Omitted if extended length messages are required. 

Delimiter

1 C

Optional.  Value ";".  Only present if extended length messages to be used.

Extended Message Length

4 H

Optional.  Only present if extended length messages are to be used.  Defines the length of the next field.  Maximum value is determined by the maximum size of the HSM input buffer.

Extended Message Text

n A

Optional.  Only present if extended length messages are to be used. The message to be authenticated as received from the terminal, but excluding the STX, ETX and LRC. The last 8 characters are assumed to be the MAC. An all zero account number cannot be used. 

End message delimiter

1C

Optional. Must be present if a message trailer is present. Value X’19.

Message trailer

n A

Optional. Maximum length 32 characters.


 

Field

Length & Type

Details

RESPONSE MESSAGE

Message header

m A

Returned to the Host unchanged.

Response code

2 A

Value RP.

Error code

2 N

00 : No errors

10 : Key register parity error

12 : No keys loaded in user storage

13 : LMK error; report to supervisor

15 : Error in input data

21 : Invalid user storage index

80 : Message length error

MAC residue

8 H

The MAC residue encrypted under LMK 10.

MAC

8 H

The generated MAC to be sent to the terminal.

End message delimiter

1C

Present only if present in the command message. Value X’19.

Message trailer

n A

Present only if present in the command message. Maximum length 32 characters.