Smart card having an optical communication circuit and a method for use thereof

A method for carrying out a secure transaction between a data transaction device a client machine, including the following steps all carried out by the client machine:

• (a) receiving a request for service,
• (b) conveying data to an optical sensor of the data transaction device as a modulated light beam via a display device of the client machine for allowing the data transaction device to display a return code derived from said data on a display unit of the data transaction device,
• (c) receiving the return code as input to the client machine by an owner of the data transaction device,
• (d) verifying the return code, and
• (e) if the return code matches a transaction code associated with the transaction or a predetermined function thereof, proceeding in accordance with the return code.

A system for carrying out a secure transaction between a data transaction device and a client machine,

• the data transaction device comprising at least one optical sensor for receiving from an application a light beam modulated with data that informs a user of the data transaction device of a return code for sending to the client machine in order to complete the transaction, and
• the client machine comprising:
• a modulator for modulating a signal representative of a light beam with data associated with a transaction code so as to form a modulated light beam signal,
• a display driver coupled to the modulator and responsive to the modulated light beam signal for illuminating a display device so that at least some pixels thereof emit a light beam that is modulated with the data,
• a verification unit for verifying a return code issued by a user of the data transaction device, and
• a transaction processor coupled to the verification unit for processing the transaction in accordance with the transaction code if the return code matches the transaction code or a function thereof.