High-security integrated-circuit card

Abstract

An integrated circuit card having a one-chip micro computer, a memory, and an address bus and data bus for coupling the micro computer and the memory, includes an input/output bus and interface for communication with an external terminal device. The micro computer executes processing commands from the external device, and returns the processing results to the external device through the interface. Instead of returning the processing results to the micro computer immediately when processing is finished, the IC card includes a timer for measuring elapsed time starting with the receipt of a processing command. The processing results are returned to the external device only when a predetermined elapsed time has been measured by the timer. Therefore, the return of the processing results, (for example, the determination as to whether a PIN is correct) is not dependent upon the processing time, making it impossible for a user of the external device to determine the type of processing command and the results of the processing based on the processing time.

Dependencies are inferred from the claim text.