Protection against information loss from telephone cards - uses memory zones and releases modified information from first to second zones with control bit

摘要

Information is stored on cards and consists of writing a bit for counting in the first zone, removal of the second zone if the writing of the first bit has been completed and the writing of at least a control bit to check that the previous step had been completed. When the card is re-written bits are verified for the control of the previous steps and a second zone will store information to allow for error in the first zone. The verification of the control bit consists in reading the state of the bit of the writing or not of the second zone. The card will count units and contains N (2) in an identical state to represent the units of use. Initially the zone is charged with N(1) bits and the number of times for authorised charging is N(1)/2), the other N (1)/2 bits are control bits. The card can be used to store telephone card information or parking-meter units. USE - Security of information stored on cards for electronic counting of user units.