Handling Interac Payments in Canada

on Jan24

With this article we continue the series of articles related to EMV standard and EMV certifications. The purpose of this particular article is to describe the peculiarities of integrations with Canadian payment service providers.

Any integration with a payment processing partner in Canada requires integration with Interac Association, which is a non-profit inter-bank debit network, connecting multiple financial entities in Canada. In principle, the process of integration with Interac is similar to integrations with other associations, such as Visa and MasterCard (or integrations with debit networks in the US). However, there are certain requirements, which distinguish integrations with Interac from those done with other associations. The difference lies in the supplemental mechanisms imposed by Interac Association members on processing of card-present and card-not-present transactions.

Let us outline these additional requirements.

Processing of card present transactions by Interac Association

When it comes to processing of card-present payments (both EMV and swipe) by Interac merchants, the distinguishing feature is the transaction validation mechanism. This mechanism involves additional data protection level. To provide this protection, an additional block of data is generated during transaction verification. This block is called message authentication code or MAC.

MAC block of data represents an encrypted line of values. These values are: transaction ID, transaction amount, merchant ID, and terminal ID. For encryption of the data block, including these values, a special key is used, called the session key. It should be stressed, that the session key is a separate value, unrelated to card PINs or P2PE keys. The session key is stored in the terminal memory and has to be updated (rotated) after a fixed number of transactions is processed. MAC values cannot be calculated at POS/gateway level, as they depend on particular terminal hardware.

Encrypted MAC block is used as a kind of digital signature/seal, which is used by the payment processor to ensure that the rest of the message arrived unaltered. When the message is received by the processor, it uses MAC block as well as values provided in the message to verify the integrity of the message. The response, generated by the processor and sent to the terminal, also includes an additional encrypted MAC block of data, which has to be decrypted and validated by the terminal. The terminal must send back confirmation of receipt of unaltered response message.

As we see, MAC ensures the control of transaction integrity. We should remind that MAC is a mechanism, specific for Interac, and intended only for protection of debit (both EMV and swiped) card data.

Processing of card-not-present transactions by Interac Association

When it comes to processing of card-not-present transactions, some (but not all) Interac Association members use an additional data protection mechanism, which is, in a way, similar to 3D secure capabilities, used by Visa and MasterCard.

More or less detailed information on how 3D secure works can be found in the respective Paylosophy article. Here we’d like to remind, that 3D secure protection mechanism redirects the cardholder from the shopping cart application to the bank’s web-site, where he is required to input some additional confirmation of his identity (usually, some confirmation code or password).

Some Canadian providers are using a special online service, similar to 3D secure. A cardholder, paying for products or services online with his debit card, is automatically redirected to the web-site of the aforementioned online service, where he is required to input additional information, confirming his identity.

Conclusion

If you are planning your first integration in Canada, it is important to understand, that, even if you have the experience of conducting integrations in the US, in Canada your integrations will be a bit more complicated, due to additional Interac logic. Particularly, this means that an EMV payment application, developed in the US, would still require quite significant adjustments to be able to support Interac in Canada, because Interac, in its turn, requires the special logic, depending on specific terminal hardware. If you are ordering test terminals to do your integrations, make sure, that they are injected not only with a PIN key, but with the MAC key, needed for integration with Interac.

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