Transaction system of the electronic purse type
First Claim
1. A transaction method for a card having a permanent write memory with at least some of its bits associated with corresponding value units, the memory being consumable by writing, wherein the memory contains a coding zone defining at least one base value from which a sequence of value units can be established, the value units being spaced apart at successive powers of two, 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 the associated value units, the method comprising the steps of:
- representing a monetary amount in binary notation on the basis of the base value;
selectively writing a value bit in each of the value words as a function of the bit of corresponding significance in the binary notation; and
writing any remaining more significant bits in the most significant value word.
1 Assignment
0 Petitions
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 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.
51 Citations
17 Claims
-
1. A transaction method for a card having a permanent write memory with at least some of its bits associated with corresponding value units, the memory being consumable by writing, wherein the memory contains a coding zone defining at least one base value from which a sequence of value units can be established, the value units being spaced apart at successive powers of two, 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 the associated value units, the method comprising the steps of:
-
representing a monetary amount in binary notation on the basis of the base value; selectively writing a value bit in each of the value words as a function of the bit of corresponding significance in the binary notation; and writing any remaining more significant bits in the most significant value word. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
-
Specification