Patent EA-000730-B1 (EA)
Title: Method for protectedly debuting an electronic payment means
Inventor: WISSENBURGH JELLE
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 number (Rl) to the payment means (11), the payment means (11), in response to said first random number (Rl), transfers a first authentication code (MAC1) to the payment station (12), which first authentication code (MAC1) is determined on the basis of at least the first random number (Rl) and a first authentication value (Al), and the payment station (12) checks the first authentication code (MAC1), and a further step (III), in which: the payment station (12) transfers a second random number (R2) to the payment means (11), the payment means (11) transfers a second authentication code (MAC2) to the payment station (12), with the second authentication code being determined on the basis of at least the second random number (R2) and a second authentication value (A2), the second authentication value (A2) being derived from the first authentication value (Al), and the payment station (12) derives the second authentication value (A2) from the first authentication value (Al) and checks the second authentication code (MAC2). 2. Method according to claim 1, wherein the first and second authentication values (Al, A2) are identical. 3. Method according to claim 2, wherein the first and second authentication values (Al, A2) comprise consecutive counter values. 4. Method according to claim 1, wherein an authentication value (e.g. A2) is each time formed on the basis of a random number (e.g. R2) and the previous authentication value (Al). 5. Method according to any of the preceding claims, comprising an intermediate step (II), 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). 6. Method according to any of the preceding claims, wherein the first random number (Rl) is equal to the second random number (R2). 7. Method according to any of the preceding claims, wherein an authentication code (e.g. MAC2) is also determined on the basis of a key and an identification code. 8. Method according to any of the preceding claims, wherein an authentication code (e.g. MAC1) is determined with the aid of a cryptographic function (F). 9. Method according to any of the preceding claims, wherein in the first and third steps (I, III) the payment means (11) transfers a balance (e.g. SI) to the payment station (12). 10. Method according to any of the preceding claims, wherein in the first and third steps (I, III) the payment means (11) transfers the current authentication value (e.g. Al) to the payment station (12). 11. Method according to any of the preceding claims, wherein the third step (III) is carried out repeatedly. 12. Method according to any of the preceding claims, further comprising a fourth step (IV) wherein the difference (S1-S2) between the balances of the first and third steps is recorded in the payment station (12). 13. Method according to any of the preceding claims, wherein the payment station (12) comprises a module for protectedly recording data. 14. Method according to any of the preceding claims, wherein the command (D) is a debiting command effecting in the second step (II) a lowering of the balance (SI) of the payment means (11).