Electronique Serge Dassault

Thierry Collin

A card (2) having a memory microcircuit (20) with access thereto under the control of a hard-wired logic circuit or a microprocessor (21) is suitable for cooperating with a terminal (1). A memory in EPROM technology (or in E.sup.2 PROM technology) includes value words (e.g., thirty-two bit words comprising twenty-five value bits, four bits for coding the value unit of each value bit, and a verification bit). By loading a plurality of words into the memory so as to set up a sequence of value units spread over successive powers of 2, the calculation means can split up the amount of any transaction less than the maximum value of the card into binary form very simply, and then consume not more than one bit per value unit (optionally other than the most significant value unit) in respect of each transaction.

Transaction system of the electronic purse type

A card (2) having a memory microcircuit (20) with access thereto under the control of a hard-wired logic circuit or a microprocessor (21) is suitable for cooperating with a terminal (1). A memory in EPROM technology (or in E.sup.2 PROM technology) includes value words (e.g., thirty-two bit words comprising twenty-five value bits, four bits for coding the value of each value bit, and a verification bit). By loading a plurality of words into the meory so as to set up a sequence of value units spread over successive powers of 2, the calculation means can split up the amount of any transaction less than the maximum value of the card into binary form very simply, and then consume not more than one bit per value unit (optionally other than the most significant value unit) in respect of each transaction.

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Courbevoie, France

Thierry Collin