| 主权项 |
1. A method comprising:
altering, by a phone, during a first payment transaction, a first data string; forming, by the phone, a second data string; forming, by the phone, a first dynamic verification value using a portion of the second formed data string; providing, by the phone, the first dynamic verification value and a primary account number to a first point of sale terminal, wherein the point of sale terminal generates a first authorization request message comprising the provided primary account number, a first transaction amount and the provided first dynamic verification value, and send the generated first authorization request message comprising the provided first dynamic verification value, the first transaction amount, the provided first dynamic verification value to a server computer; wherein the server computer then verifies the first dynamic verification value, and receives an authorization response message from the server computer approving of the first payment transaction; altering, by the phone, during a second payment transaction, the formed second data string; forming, by the phone, a third data string; forming, by the phone, a second dynamic verification value using a portion of the third data string; providing, by the phone, the formed second dynamic verification value and the provided primary account number to a second point of sale terminal; wherein the second point of sale terminal generates a second authorization request message comprising the provided primary account number, a second transaction amount, and the formed second dynamic verification value and sends the second authorization request message comprising the provided primary account number, the second transaction amount, and the second dynamic verification value to the server computer; and wherein the server computer verifies the second dynamic verification value, and receives a second authorization response message approving the second payment transaction. |
