Transaction system of the electronic purse type
First Claim
1. A transaction system of the type comprising at least one terminal and a microcircuit card suitable for cooperating with the terminal, said card including a permanent write memory having at least some of its bits associated with corresponding value units, said memory being consumable by writing, wherein the memory contains a coding zone for defining at least one base value from which a sequence of value units can be established, said value units being spaced apart at successive powers of 2, together with a plurality of value words each associated with one of the value units, and each containing a predetermined number of value bits each possessing a value equal to said value unit, and wherein the system includes calculation means suitable for splitting up a monetary amount into binary notation on the basis of said base value, and for issuing commands to write or not to write a value bit in each of said value words as a function of the bit of corresponding significance in said binary notation, and for writing any remaining more significant bits most significant value word.
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Accused Products
Abstract
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 E2 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.
202 Citations
18 Claims
- 1. A transaction system of the type comprising at least one terminal and a microcircuit card suitable for cooperating with the terminal, said card including a permanent write memory having at least some of its bits associated with corresponding value units, said memory being consumable by writing, wherein the memory contains a coding zone for defining at least one base value from which a sequence of value units can be established, said value units being spaced apart at successive powers of 2, together with a plurality of value words each associated with one of the value units, and each containing a predetermined number of value bits each possessing a value equal to said value unit, and wherein the system includes calculation means suitable for splitting up a monetary amount into binary notation on the basis of said base value, and for issuing commands to write or not to write a value bit in each of said value words as a function of the bit of corresponding significance in said binary notation, and for writing any remaining more significant bits most significant value word.
Specification