What are selectable kernel configurations and when might selectable kernel configurations be used?

Selectable kernel configurations are optional terminal features that allow terminals to support different capabilities for different transactions. For example, if allowed by the payment system, a terminal might support only ‘No CVM Required’ for low value transactions and support Signature and Offline PIN for higher value transactions.  Previously the EMV specifications mandated that Terminal Capabilities be initialized before the terminal was placed in its operational state thus disallowing this transaction-by-transaction change.  Selectable kernel configurations allow terminals to invoke appropriate type-approved kernel configurations dynamically in order to support the required terminal capabilities on a transaction-by-transaction basis.  The determination of the invoked kernel configuration is based on characteristics of the transaction and the card, such as RID or AID and the transaction amount.

The selectable kernel configurations specification update defined rules around this switching of terminal capabilities:

  • All kernel configurations that can be selected must have been type approved.
  • The selection of the kernel configuration must occur before the GET PROCESSING OPTIONS command.  This means Terminal Type, Terminal Capabilities, and Additional Terminal Capabilities will accurately reflect the behavior of the terminal if passed to the card in the GET PROCESSING OPTIONS command.

Terminal support for selectable kernel configurations is optional.

The following are some other examples where selectable kernel configurations might be used:

  • An Automated Teller Machine (ATM) that also sells train tickets.  When the cardholder selects the cash option, the Terminal Capabilities would indicate CVM support for Online PIN only and no support for offline data authentication. The Terminal Type would be ’14’ (online-only). When the cardholder selects the ticket option, the Terminal Capabilities may indicate support for Offline PIN and offline data authentication with a terminal Type of ’15’ (offline with online capability).
  • POS terminals in a country must support Online PIN for transactions being routed through a country’s domestic debit network but must not support Online PIN for transactions routed through networks that do not support Online PIN.  Terminal Capabilities could support Online PIN when the selected AID is for the domestic debit network but not have this support when the selected AID is for the other network.

Please note that the individual payment systems may have rules/requirements governing whether, and for what purpose, selectable kernel configurations may be used.

In relation to the U.S. implementation and support of EMV debit transactions, the selectable kernel can be applied as outlined in the EMV Migration Forum Debit Technical Working Committee – U.S. Debit EMV Technical Proposal document:

6.3.2 CVM using the Credit/Debit Button

For merchants using the credit/debit button, this will require support for a Selectable Kernel but not support for PIN cancel. Merchants who decide to support this Selectable Kernel should consult their device manufacturer on how this will be supported.

The consumer choice and IIN (BIN) provided in the FCI prior to the final application selection may drive a Selectable Kernel to use the U.S. common AID or international AID. Alternatively, a merchant offering consumer choice (i.e., cardholder confirmation) should display the Application Label of each AID as a cardholder selection choice. Note, Application Labels are only available after the PSE/FCI of each application has been read. The EMV Terminal Capabilities of the Selectable Kernel are defined at the transaction level.

As an alternative to using Selectable Kernel, the merchant has the option to select the International AID when the credit button is selected by the consumer and the Common AID for the debit button.