METHOD ENABLING A PURCHASER TO ASK FOR THE EXECUTION OF AN OBLIGATION RELATED TO A CARD AND ENABLING AN EMITTER TO RECOGNIZE SAID OBLIGATION

摘要

1. A method for a cardholder to request fulfillment of an obligation associated with a card and for an issuer to acknowledge this obligation, comprising issue of cards each having an identifier and with each an obligation of the issuer being associated, reading the identifier from the card by the cardholder, the cardholder's presenting to the issuer the identifier read from the card and directions specifying fulfillment of the obligation associated with the card, the issuer's verifying the validity of the card using the identifier and directions presented by the cardholder, and the issuer's acknowledgment of the obligation corresponding to the obligation associated with the card and the cardholder's directions, characterized in that one issues cards each additionally having the verifier corresponding to the identifier and concealed, at least partly, by a masking device, the issuer, when verifying the validity of the card using the identifier and directions presented by the cardholder, checks that the issuer has not presented previously a signed reply binding the identifier presented by the cardholder and directions different from the directions presented by the cardholder, forms a reply to the cardholder, which reply binds the identifier and directions presented, signs the formed reply, and presents the signed reply to the cardholder, the cardholder, having received the signed reply presented by the issuer, verifies the signature on the reply and checks that the signed reply binds the identifier and directions presented by the cardholder to the issuer, after which the cardholder reads the verifier from the card and presents the verifier to the issuer, who, having received the verifier, checks that the verifier presented by the cardholder corresponds to the identifier presented by the cardholder, thus completing the verification of validity of the card. 2. The method of claim 1, characterized in that when the cards are issued, the identifiers of the cards are chosen so that the probability that randomly chosen data coincide with the identifier of an issued card is less than some prescribed probability. 3. The method of claim 1, characterized in that one issues cards with identifier concealed, at least partly, by a masking device. 4. The method of claim 3, characterized in that one issues cards such that opening the masking device of the verifier of the card leads to opening the masking device of the identifier. 5. The method of claim 3, characterized in that when reading the identifier from the card, the cardholder opens one of the card masking devices, reads the data that were concealed by the opened masking device, and uses these data as an identifier. 6. The method of claim 1, characterized in that one issues cards consisting of several parts with additional data determining the correspondence between the parts of the card. 7. The method of claim 1, characterized in that when verifying the validity of the card using the identifier and directions presented by the cardholder, the issuer additionally checks that the presented identifier coincides with the identifier of an issued card. 8. The method of claim 1, characterized in that a digital signature is used to sign the formed reply. 9. The method of claim 1, characterized in that the identifier read from the card and the directions specifying fulfillment of the obligation associated with the card are presented to the issuer via electronic means of communication. 10. The method of claim 1, characterized in that the signed reply is presented to the cardholder via electronic means of communication. 11. The method of claim 1, characterized in that the verifier is presented to the issuer via electronic means of communication. 12. The method of claim 1, characterized in that when the cardholder presents to the issuer the identifier read from the card and the directions specifying fulfillment of the obligation associated with the card, the identifier and the directions are encrypted. 13. The method of claim 1, characterized in that when the cardholder presents to the issuer the identifier read from the card and the directions specifying fulfillment of the obligation associated with the card, the issuer is additionally presented with an encryption key, which the issuer uses for encrypting the signed reply to the cardholder. 14. The method of claim 1, characterized in that the directions specifying fulfillment of the obligation associated with the card include identification data of the entity additionally controlling fulfillment of the acknowledged obligation. 15. The method of claim 14, characterized in that the identification data of the entity additionally controlling fulfillment of the acknowledged obligation include a public key of the entity in a predetermined digital signature system. 16. The method of claim 1, characterized in that along with the verifier of the card, the cardholder repeatedly presents to the issuer the identifier of the card or a part of it. 17. The method of claim 1, characterized in that when verifying the validity of the card using the identifier and directions presented by the cardholder, the issuer additionally checks that the directions presented by the cardholder meets some predetermined criteria. 18. The method of claim 1, characterized in that when checking that the issuer has not earlier presented to anybody a signed reply binding the identifier presented by the cardholder and directions different from that presented by the cardholder, the issuer disregards any earlier presented reply if the signature on the reply has become invalid, and the obligation associated with the card whose identifier is bound to the directions by this reply is not acknowledged.