Patent attributes
A payment terminal includes a card interface and a transaction processor. The terminal receives a preliminary authorization amount, and receives application data from a payment card that is interfaced with the card interface. The application data includes an account number that is uniquely associated with the payment card. The processor generates an adjusted authorization amount from the account number and the preliminary authorization amount, determines whether the adjusted authorization amount can be authorized offline, and transmits a cryptogram request to the payment card. The adjusted authorization amount is different from the preliminary authorization amount. The cryptogram request includes the adjusted authorization amount. The processor receives a cryptogram from the payment card, receives an authorization response message confirming authorization of the adjusted authorization amount, and confirms that the cryptogram was generated from the adjusted authorization amount and from a cryptographic key that is uniquely associated with the payment card.
