Patent EA-000857-B1 (EA)
Title: Method of debiting an electronic payment means
Inventor: PIETERSE ROB
IPC: G07F7/08
Filed: 1996-11-14
Abstract: 1. Method of protectedly performing a transaction using an electronic payment means (11) and a payment station (12), the method comprising: - an initial step (I), in which: - the payment station (12) transfers a first random value (R1) to the payment means (11), - the payment means (11), in response to said first random value (R1), transfers a first authentication code (MAC1) to the payment station (12), which authentication code is determined on the basis of at least a first start value (Q1), a first random value (R1) and first transaction data (S1) of the payment means (11) using a predetermined process (F), the process further producing a first end value (Y1), - a further step (III), in which: - the payment station (12) transfers a second random value (R2) to the payment means (11), - the payment means (11) transfers a second authentication code (MAC2) to the payment station (12), which authentication code is determined on the basis of at least a second start value (Q2), the second random value (R2) and second transaction data (S2) of the payment means (11) using said process (F), the second start value (Q2) being based on the first end value (Y1). 2. Method according to claim 1, wherein the second start value (Q2) is identical to the first end value (Y1). 3. Method according to claim 1 or 2, wherein an authentication code (e.g. MAC1) is also determined on the basis of a key (K) and/or an identification code. 4. Method according to claim 1, 2 or 3, comprising an optional intermediate step (II) carried out between the initial (I) and further (III) steps, in which: - the payment station (12) transfers a command (D) to the payment means (11), and a balance of the payment means (11) is changed on the basis of the command (D). 5. Method according to any of the preceding claims, wherein the first random value (R1) and the second random value (R2) are identical, the substep of the payment station (12) transferring the second random value (R2) to the payment means (11) being omitted. 6. Method according to any of the preceding claims, wherein the process (F) involves a cryptographic function. 7. Method according to any of the preceding claims, further comprising a fourth step (IV), in which: - the payment station (12) records the difference (S1-S2) between the balances of the first and third steps. 8. Method according to any of the preceding claims, wherein the third step (III) is carried out repeatedly. 9. Method according to any of the preceding claims, wherein the payment station (12) comprises a module for protectedly recording data. 10. Payment means (11) according to any of the preceding claims, wherein the balances in the payment means are stored in the first memory (101) permitting repeated write actions, and an authentication code (MAC), as a function of a random number (R) being generated in the payment means in the second dynamic memory (104), wherein a balance (S) is recorded to the first memory (101) using as a function of a random number (R) as a function of a random number (R) repeated write actions and such clock pulses (.alpha.) that the contents of the second, dynamic memory (104) are maintained. 11. Payment means according to claim 10, wherein the number of write actions per written balance amounts to between 50 and 150. 12. Payment means according to claim 10 or 11, wherein the frequency of the clock pulses (.alpha.) is increased between write actions. 13. Payment means according to claim 10 to 12, wherein the clock pulses (alpha) have an asymmetric 1/0 ratio.