Abstract: A method and system which provides communication between a first portable device and a second portable device. The first portable device stores a first sequence number and a first key, and the second portable device stores a second sequence number and a second key. Verification is performed using the first and second keys. The first sequence number is compared to the second sequence number. If the second sequence number is newer than the first sequence number, the first sequence number is set to have a value of the second sequence number if the verification succeeds. If the first sequence number is newer than the second sequence number, the second sequence number is set to have a value of the first sequence number if verification succeeds.

Abstract: A microprocessor-based device having a memory unit and a processing unit operatively coupled to the memory unit. The memory unit has one or more risk parameters stored therein, and the processing unit is capable of performing real-time risk management analysis of transactions performed by the IC card using the risk parameters. Preferably, the microprocessor-based device is an IC card.

Abstract: A technique for representing behavioral patterns indicating fraudulent electronic cash transactions through micro-dynamic simulation of an electronic cash transaction system implementable using smart cards with embedded microcomputers. The electronic cash transaction system is stochastically modeled by four categories of agents corresponding to the participants in an electronic cash transaction economy. Some categories of agents are further subdivided into segments that have different characteristics, including the circle of other agents with whom they regularly conduct electronic cash transactions. Agents with counterfeit or fraudulent smart cards may form a segment in the simulation to allow the effects of the counterfeit or fraudulent electronic cash transactions in the complete system to be observed.