Interfacing with cards

The C-TAP specification provide interfaces to different types of cards technologies (magnetic stripe, EMV smart cards with contact and contactless including applications on smartphones).

While for EMV contact cards, one EMV kernel reads all EMV cards, presently vendors will integrate multiple scheme-specific contactless kernels.

To reflect the merchant’s business decisions, the key element in C-TAP is dynamic recognition of multiple card brands supporting flexible and parameterised defined brand-to-acquirer associations

The C-TAP application manages multiple card services and interconnects with the cards' kernels. The application controls the interactions with the secure pinpad, the cardholder and merchant displays as well as the receipt printer.

The merchant's functionality can be driven from an Electronic Cash Register or POS configuration. 

The C-TAP specification describe the messaging between terminal and acquirer.

Each acquirer can customise the transaction processing by loading its specific parameters in the terminal.

For payments, there is an exchange in 4 messages (one dialogue for authorisation and one for completion). 

A data dictionary drives the messaging formats. The present notation is Tag-Lenght-Value ("TLV" as for EMV). An alternative notation in ISO20022 is possible if a business purpose is demonstrated.
A terminal will handle multiple session with multiple acquirers, as driven by the card recognition and brand-to-acquirer associations.

A merchant can add brands to support or modify relationships with acquirers. No changes of hardware,software or configuration are required at terminal level.