Abstract: A payment processing system is discloses. The system comprises a module configured to receive a payment request for a payment transaction from one of a plurality of different merchant applications associated with a computing device wherein the request comprises payment information comprising a merchant code or transaction identifier; in response to receiving the payment request, receive encrypted payment data from a reader coupled to the computing device wherein the payment data comprises an account number associated with a user wherein the account number is encrypted according to a first key; and transmit the payment information and the encrypted payment data to a payment server.