Command:

Validate the S₄ MAC for new terminals.

Notes:

Use of this command requires the optional ESP licence. Error code 67 will be returned if the command is not licensed.

This command does not check the contents of the data block over which the MAC is generated. It is the responsibility of the user of the command to ensure the data format is correct.

Field

Length & Type

Details

COMMAND MESSAGE

Message Header

m A

Will be returned to the Host unchanged

Command Code

2 A

Value “X2”

*KMAC_S4

32 H

Double length KMAC_S4 encrypted under LMK pair 20-21 variant 7

S₄

16 H

Signature for verification

ID_PSAM

4 B

Identifier for a PSAM

ID_BATCH

2 B

Identifier for a POS Transaction Batch

NT_BATCH

2 B

The number of payment and cancellation transactions in this batch

Data Length

3 N

Length in bytes of the following data block

Data Block D₄

n B

Binary data block

End Message Delimiter

1 C

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

Message Trailer

n A

Optional. Maximum length 32 characters

RESPONSE MESSAGE

Message Header

m A

Will be returned to the Host unchanged

Response Code

2 A

Value “X3”

Error Code

2 N

00 – No error. S₄ validated successfully

01 – S₄ validation failed.

10 – KMAC 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

70 – Data D₄ length error

End Message Delimiter

1 C

Will only be present if present in the command message. Value X'19

Message Trailer

n A

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