The HSM supports the functions to load and unload value from Visa Cash cards.
Notes:
The use of the ALGLIEP and VKLIEP fields in following commands deserves special mention as these fields are optional. There are three scenarios controlled by these fields.
|
Scenario |
Applicable Visa Cash cards |
Single or Double length KDL used |
Additional Notes |
|
Neither VKLIEP or ALGLIEP supplied to HSM |
Version 1.5 and earlier DES cards |
Single |
May be used with cards which do not report VKLIEP or ALGLIEP. Backwards compatible with earlier versions of HSM firmware
|
|
Only VKLIEP supplied to HSM |
Version 1.6 DES cards and Public Key cards |
Double |
May be used with later cards. Host must determine the value of ALGLIEP and supply VKLIEP if required. Backwards compatible with earlier versions of HSM firmware |
|
Both VKLIEP and ALGLIEP supplied to HSM |
Any card. |
Single if ALGLIEP has value 01, double if ALGLIEP has value 04 |
Allows host to send both ALGLIEP and VKLIEP without concern about their values. VKLIEP must always be supplied as a placeholder even if its value is not relevant (ie when ALGLIEP is of value 01) |
This set of scenarios accommodates all relevant combinations of Visa Cash cards and allows the host application to operate in one of two modes.
· Host makes the decision about what ALGLIEP is relevant for the current transaction and either supplies VKLIEP if ALGLIEP is of value 04, or does not supply VKLIEP if ALGLIEP is of value 01. ALGLIEP itself is not sent to the HSM. Thus the first and second scenarios in the above table can be used to cater for all cards in use. This mode of operation is used by some (earlier) host systems and therefore must be supported for backwards compatibility. Note that earlier Visa Cash cards do not report a value of ALGLIEP and so the host may have to determine this in other ways. Reference 4 discusses this point.
· Host simply passes values of ALGLIEP and VKLIEP to HSM as supplied in the current transaction. Thus if a card does not supply ALGLIEP or VKLIEP no values are passed to the HSM and vice versa. Thus the first and third scenarios in the above table will be used. In this mode of operation the host is not required to make any decisions about the transaction; these are left to the HSM.
If Visa specifies alternative processing requirements in the future (and hence values of ALGLIEP other than 1 or 4) the HSM will be upgraded to accommodate them.
The earlier Visa Cash cards which do not report ALGLIEP or VKLIEP will all eventually expire making the first scenario in the above table redundant.