Importance

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Abstract

There is disclosed a method and system for conducting secure credit and debit card transactions between a customer and a merchant. The customer is issued with a pseudorandom security string by a host computer, the security string being sent to the customer's mobile telephone. A cryptographic algorithm running in a SIM card of the mobile telephone performs a hash on the security string or the One Time Code extracted from the security string, a customer PIN and a transaction amount, these last two items being entered by way of a keypad of the mobile telephone. A three-digit response code is generated by the algorithm and then passed to the merchant. The merchant then transmits the response code, transaction amount and a customer account number (card number) to the host computer, where the pseudorandom security string and PIN are retrieved from memory. The host computer then applies the same algorithm to the security string, PIN and transaction amount so as to generate a check code, and if the check code matches the response code transmitted by the merchant, the transaction is authorised. Embodiments of the present invention make use of existing CVV2 security infrastructure, but provide a significantly greater degree of security. Embodiments of the present invention may be used with ordinary face-to-face or telephone transactions, and also in e-commerce (web-based) and m-commerce (mobile telephone-based) transactions.

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First Claim