Patent ID: 8805746

Claim:
A method of purchasing an item from a merchant server computer by a user over a wireless telecommunications network using a mobile telephone handset equipped with a subscriber identification module (SIM), said method comprising: formulating a draw request message, by said SIM, that includes a purchase amount of an item and an identifier of a smart card that is in communication with said handset via a card reader interface; sending, by said SIM, said draw request message over a telecommunications network through the handset to a payment server computer associated with a merchant server computer; receiving a debit message, by said smart card, from said payment server computer that includes a cryptographic signature S 2 resulting from a first cryptographic key shared between the smart card and its issuer, and an approval to debit said smart card by said purchase amount; verifying, by said smart card, said cryptographic signature S 2 using said first shared cryptographic key; debiting, by said smart card, a stored-value application of said smart card by said purchase amount; sending, by said smart card, a debit result message to said payment server computer that includes a cryptographic signature S 3 resulting from a second cryptographic key shared between the smart card and its issuer, said signature S 3 uniquely identifying said smart card and indicating that said stored-value application of said smart card has been debited by said purchase amount; and receiving said item by said user.