Formation of AB and CD Fields from CARD DATA

The AB and CD fields are derived from the data on the magnetic stripe of the plastic card. There are variations in the way the data is derived. The Acquirer Host and Card Issuer Host systems must match the method implemented on the Terminal. It is the responsibility of the Host to obtain the AB and CD fields and submit them to the HSM in the Host command format. Typically, the fields are derived from an ISO 3554 card as follows:

Where:

                        SS                      :                       Start Sentinel.

PAN                    :                       Primary Account Number.

CFS                    :                       Card Field Separator.

4 CHRS               :                       Four characters.

DISC.DATA         :                       Discretionary Data.

ES                      :                       End Sentinel.

LRC                    :                       Longitudinal Redundancy Check.