Chip card based payment system having an on-card flag for specifying proper completion of a prior card balance replenishment session

Abstract

Improved integrity of a payment system for paying for services or goods, for example, telephone facilities, through use of electronic payment cards. In any session to increase a card balance, a “flag” is placed (“1”) on the payment card which indicates that the session must not be interrupted. After completion, the flag is removed again (“0”). A session to pay for the product or the service or to increase the balance can only be established if the flag is absent (“0”) indicating that the last session to increase the balance was correctly completed. If, on the other hand, the flag is still “1” at the start of a session, a correction routine is first performed in which the previous session to increase the balance is then correctly concluded to prevent the flag being removed by fraud, the flag can only be removed by a central system (PSTN/ABS) through issurance of an authorized instruction.

I claim:  
     
       1. A payment system comprising:  a terminal;  arranged to communicate with a payment card for communicatively interacting with the terminal  so as to effectuate a transaction therethrough; 
       means, operative in conjunction with a balance process which increases a balance stored in the payment card, for  to carry out the following tasks:  
       changing a symbol stored in the payment card from a first symbol value to a second symbol, wherein  value at the beginning of said balance process;  
         changing said symbol stored in said payment card from said second symbol value into said first symbol value at the end of said balance process;  said changing  means also being arranged to carry out the following tasks during a further process with the payment card:  
       detectsdetecting, at a beginning of said further process, if said first or said second symbol value is stored in the payment card;  
       
         if said second  symbol is stored, changes said second symbol to said first symbol and performs said process to increase the stored balance; and  has said first symbol value, continuing with said further process;  
       
       if said first  symbol is stored, indicates  has a second value, indicating that a previous execution of said balance process was interrupted prior to completion and completes or repeats  starting a terminating process to change said second symbol value into said first symbol value;  
       
         wherein the system also comprises an administration system and the system is arranged to:  
       
       
         store information regard the balance process during the execution of the balance process in said administration system;  
       
         complete or repeat  the previous execution of the balance process during said terminating process in said further process on the basis of said information still present in the administration system; and  
       
         continue said further process after said terminating process.  
       
     
     
       2. The payment system in claim  1  further comprising a central system connected to the terminal, the terminal being remote from the central system, wherein the central system, upon completion of the balance process to increase the balance stored in the card,  sends a signal to the terminal so as to change the stored symbol from the first  second symbol value to the second  first symbol value. 
     
     
       3. The payment system in claim  2  wherein at the beginning of the balance process to increase the balance stored in the card,  the terminal changes the stored symbol from the second  first symbol value to the first  second symbol value. 
     
     
       4. The payment system in claim  3 comprising a payment card wherein the payment card comprises an electrically erasable programmable read only memory (EEPROM) and the stored symbol is changed from the secondfirst symbol value to the firstsecond symbol value as a result of a WRITE instruction executed by the card. 
     
     
       5. The payment system in claim  2 comprising a payment card, wherein the payment card comprises an electrically erasable programmable read only memory (EEPROM) and the stored symbol is changed from the firstsecond symbol value to the secondfirst symbol value as a result of a MODIFY instruction executed by the card. 
     
     
       6. A method for use in a payment system having a terminal and a payment card, wherein the payment card communicatively interacts with the terminal so as to effectuate a transaction therethrough, the method comprising the steps of: 
       changing, in conjunction with a balance process which increases a balance stored in the payment card, a symbol stored in the card from a first symbol value to a second symbol value at the beginning of said balance process;  
         changing said symbol stored in said payment card from said second symbol value into said first symbol value at the end of said balance process, said method also  comprising the following steps ofduring a further process with the payment card:  
       detecting, at a beginning of said further process, if said first or said second symbol value is stored in the payment card;  
       if said second  symbol is stored, changing said second symbol to  has said first symbol and performing said process to increase the stored balance  value, continuing with said further process; and  
       if said first  symbol is stored  has said second symbol value, indicating that a previous execution of said balance process was interrupted prior to completion and starting a terminating process to change said second symbol value into said first symbol value,  
       
         wherein the method also comprises the steps of:  
       
       
         storing information regarding the balance process during the execution of the balance process in an administration system;  
       
       completing or repeating the previous execution of the balance process during said terminating process in said further process on the basis of said information still present in the administration system; and  
       
         continuing said further process after said terminating process.  
       
     
     
       7. The method in claim  6  further comprising the step of sending a signal, from a central system to the card and upon completion of the balance process to increase the balance stored in the card,  so as to change the stored symbol from the first  second symbol value to the second  first symbol value. 
     
     
       8. The method in claim  7  further comprising the step of changing, at the beginning of the balance process to increase the balance stored in the card,  the stored symbol from the second  first symbol value to the first  second symbol value by means of said terminal. 
     
     
       9. The method in claim  8  further comprising the step of changing the stored symbol from the second  first symbol value to the first  second symbol value as a result of a WRITE instruction executed by the card. 
     
     
       10. The method in claim  7  further comprising the step of changing the stored symbol from the first  second symbol value to the second  first symbol value as a result of a MODIFY instruction executed by the card.