Method and system using a bitmap for passing contactless payment card transaction variables in standardized data formats
An electronic payment system is configured to process both proximity payment card type and magnetic stripe card type transactions. The magnetic stripe card transaction data is communicated between cards, readers, and transactions authorizing or approving parties in common industry ISO 7811 standard data structures or tracks. The proximity payment card transaction data such a dynamic authentication codes are placed in unused space in the same standard formatted data structures. The availability of unused space varies with card issuer or vendor. An issuer-specific bitmap provides an index to the available space in discretionary data fields in magnetic stripe tracks. The bitmap also is stored in the card's discretionary data field.
1. A mobile device for integrating proximity payment transaction parameters for a payment-by-proximity transaction in an industry standard—ISO-7811—formatted data structure, wherein said data structure comprises at least one of industry-standard Track 1, Track 2 and Track 3 magnetic card data structures, such that said proximity payment transaction parameters are in a format compatible with an electronic payment system infrastructure for processing magnetic stripe card payment transactions, the mobile device comprising:
a) an antenna;
b) a memory device storing a bitmap, wherein said bitmap identifies positions in a discretionary data field of a magnetic card industry standard formatted data structure associated with said mobile device;
c) a processing unit coupled to said antenna and said memory device, arranged to contactlessly transmit to a proximity payment terminal said bitmap for placing proximity payment transaction parameters in said discretionary data field of said industry standard magnetic card formatted data structure at positions identified by said bitmap, and further wherein the resulting electronic proximity payment transaction processing message generated by said proximity payment terminal using said bitmap is in a standard magnetic stripe format compatible with electronic payment system infrastructure for processing magnetic stripe card payment transactions and so that the payment-by-proximity transaction is processed by said electronic payment system infrastructure as if the payment-by-proximity transaction is a standard magnetic stripe card payment transaction.
2. The mobile device of claim 1 wherein said processing unit is arranged to calculate a dynamic authentication code (CVC3) as part of said proximity payment transaction parameters.
3. The mobile device of claim 2 wherein the proximity payment transaction parameters further comprise at least one of an application transaction counter (ATC) and an unpredictable number (UN), and wherein said bitmap identifies positions in said standard magnetic stripe format for placing at least a portion of said dynamic authentication code and at least a portion of said at least one of said ATC and said UN.
4. The mobile device of claim 2 wherein said processing unit is arranged to:
receive an unpredictable number (UN) from said antenna;
wherein said CVC3 is computed based on a portion of the received unpredictable number (UN); and
communicates at least a portion of the computed dynamic authentication code (CVC3) value to the antenna for reception by a terminal and subsequent placement in the discretionary data field in the Track.
5. The mobile device of claim 4 wherein CVC3 is further computed based on at least a portion of an automatic transaction counter (ATC) and wherein said processing unit is further arranged to transmit at least a portion of said ATC to the antenna for reception by said terminal and subsequent placement in the discretionary data field in the Track.
6. The mobile device of claim 1 wherein the proximity payment transaction parameters relate to a transaction between said mobile device and a terminal, wherein said terminal uses processes to place the card transaction parameters in the discretionary data field in a Track at positions identified by the bitmap.
7. The mobile device of claim 1 wherein said antenna receives from said proximity payment card terminal data representing an unpredictable number having a number of non-zero digits, wherein said number of non-zero digits are determined based on a portion of said static bitmap and wherein payment card transaction parameters are based at least in part on said unpredictable number.
8. The mobile device of claim 1 , wherein the bitmap comprises two bytes which identify positions in a 13 digit discretionary data field in a Track 2 magnetic stripe data format.
9. The mobile device of claim 1 , wherein the memory device is contained in the processing unit.
10. The mobile device of claim 1 , wherein the processing unit comprises a Secure Element.