US Patent 9858572 Dynamic alteration of track data

Using discretionary data fields to secure transactions comprises a payment system employing a server configured to associate a payment account of a user with a user computing device, the payment account comprising a payment account identifier that identifies the payment account, and establish a authentication challenge and an corresponding challenge response. The payment system receives a first payment authorization request originating from a merchant computing system comprising the payment account identifier, data associated with the payment account identifier, and a request to fund a transaction using the payment account, wherein the data associated with the payment account identifier comprises a challenge response provided by the user computing device located in a discretionary data field. The payment system compares the provided challenge response with the corresponding challenge response, and approves the transaction based on whether the provided challenge response and the corresponding challenge response match.