Method and apparatus for settlement of accounts by IC cards

A method of settling charges resulting from use of an IC card that has been issued from a management center through an IC card dispenser and that has been used to obtain a service at an IC card terminal, said IC card having card information memory means into which are written from said management center a master public key nA for verifying a master digital signature SA created by said management center by use of master keys pA and qA, card secret keys pU and qU for enabling said IC card to create a digital signature, a card public key nU for verifying said digital signature created by said IC card, and a card identification number IDU and a first master digital signature SA1 created by use of said master keys pA and qA for information including said card public key nU and said card identification number IDU, said IC card terminal having terminal information memory means into which are written from said management center said master public key nA, terminal secret keys pT and qT for enabling said IC card terminal to create a digital signature, a terminal public key nT for verifying said digital signature created by said IC card terminal, a terminal identification number IDT and a second master digital signature SA2 created by use of said master keys pA and qA for information including said terminal public key nT and said terminal identification number IDT, said method comprising:

• a step wherein said IC card transmits said card public key nU, said card identification number IDU and said first master digital signature SA1 to said IC card terminal;
• a step wherein said IC card terminal verifies the first master digital signature SA1 received from said IC card and, if it is valid, transmits said terminal public key nT, said terminal identification number IDT and said second master digital signature SA2 to said IC card;
• a step wherein said IC card verifies said second master digital signature SA2 received from said IC card terminal and, if it is valid, transmits information corresponding to a current remaining amount value V to said IC card terminal;
• a step wherein said IC card terminal makes a check to see if said information corresponding to said current remaining value V is adequate to pay for a requested service and, if it is adequate, the IC card terminal becomes enabled for providing the service;
• a step wherein, after completion of said service, said IC card terminal creates an updated remaining value V' and generates a terminal digital signature ST for information including said updated remaining value V' and then transmits said terminal digital signature ST to said IC card together with said updated remaining value V';
• and
• a step wherein said IC card verifies the terminal digital signature ST received from said IC card terminal.