Security system incorporating mobile device

A method comprising:

• receiving, at a server computer over a secure communications channel, a first request from a mobile device for a device verification value, the first request including account information associated with a portable consumer device and information associated with the mobile device, wherein the first request is based on an interaction between the mobile device and the portable consumer device;
• performing, by the server computer, a first validation test pertaining to the first request to validate the mobile device;
• generating, by the server computer, a first device verification value based on at least the first validation test, wherein the first device verification value is a temporary first device verification value that is valid for a first predetermined number of transactions or for a first predetermined amount of time, wherein the temporary first device verification value includes information related to validation of at least the mobile device;
• sending, by the server computer, the first device verification value to the mobile device;
• storing, by the server computer, the first device verification value;
• receiving, at the server computer, a first authorization request message comprising the first device verification value and the account information associated with the portable consumer device from a first point of sale terminal for a transaction between the mobile device and the first point of sale terminal, wherein the first device verification value was previously transferred from the mobile device to the first point of sale terminal via an interaction between the mobile device and the first point of sale terminal, wherein the account information was previously transferred from the portable consumer device to the first point of sale terminal via an interaction between the portable consumer device and the first point of sale terminal;
• determining, by the server computer, whether the first device verification value in the first authorization request message corresponds to the stored first device verification value;
• generating, by the server computer, a first authorization response message based at least in part on whether the first device verification value in the first authorization request message corresponds to the stored first device verification value;
• and
• sending the first authorization response message to the first point of sale terminal;
• generating, by the server computer, a second device verification value after the first device verification value becomes invalid and based on another interaction between the mobile device and the portable consumer device;
• and
• sending, by the server computer, the second device verification value to the mobile device.