Authentication of an electromagnetic terminal-transponder couple by the transponder

• US 8,446,259 B2
• Filed: 06/15/2010
• Issued: 05/21/2013
• Est. Priority Date: 06/25/2009
• Status: Active Grant

• Current Assignee: STMicroelectronics SAS (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SAS (STMicroelectronics NV)
• Inventors: Wuidart, Luc
• Primary Examiner(s): Bugg, George
• Assistant Examiner(s): Akhter, Sharmin
• Application Number:
  US12/815,695
• Publication Number:
  US 20100328026A1
• Time in Patent Office: 1,071 Days
• Field of Search: 340 461- 462, 340/5.2, 340/5.21, 340/5.8, 340 581- 586, 340/5.66, 340/7.28, 340 101- 1211, 340/16.1, 3405721-5729, 340/635, 340/636.11, 340/636.12, 340/636.13, 340/636.15, 340/645, 340657-658, 340660-664, 340/854.8, 340/870.18
• US Class Current: 340/10.4
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 19/07336 Active means, e.g. jamming or scrambling of the electromagnetic field

Abstract

A method of authentication of a terminal generating a magnetic field, by a transponder including an oscillating circuit from which a D.C. voltage is generated, wherein the transponder: receives first data relative to the current in an oscillating circuit of the terminal, measured by the terminal for a first value of the resistive load of the transponder; and exploits these first data and second data relative to the level of said D.C. voltage, respectively measured for the first resistive load value and for a second resistive load value.

Claims

1. A method of authentication of a terminal generating a magnetic field, by a transponder comprising an oscillating circuit from which a D.C. voltage is generated, wherein the transponder:

receives first data relative to a current in an oscillating circuit of the terminal, measured by the terminal for a first value of a resistive load of the transponder;

exploits the first data, and second data relative to levels of said D.C. voltage, the levels of the D.C. voltage respectively measured for said first resistive load value and for a second resistive load value; and

determines an authenticity of the terminal based on a result of the exploiting.

2. The method of claim 1, wherein exploiting the first data comprises:

evaluating, based on said second data, a ratio between values of the current in the oscillating circuit of the terminal; and

comparing this ratio with said first data.

3. The method of claim 1, wherein exploiting the first data comprises:

evaluating, based on said first data, a value of said D.C. voltage; and

comparing this evaluated value with the level of said D.C. voltage measured for the second resistive load value.

4. The method of claim 1, wherein the first data correspond to a ratio of a value of the current in the oscillating circuit of the terminal while no transponder is present in its field to a value of this current with the first resistive load value of the transponder.

5. The method of claim 1, wherein in the absence of a determination that the terminal is authentic, the transponder sends incorrect data.

6. A method for authenticating a terminal generating a magnetic field and a transponder which is present in this field, wherein:

the terminal is authenticated by the transponder according to claim 1; and

to authenticate the transponder, the terminal;

receives third data relative to the current in the oscillating circuit of the terminal, evaluated for a second value of the resistive load of the transponder;

compares the third data with fourth corresponding data obtained by measurement; and

determines an authenticity of the transponder based on a result of the comparing.

7. The method of claim 6, wherein the third and fourth data are ratios of a value of a current in the oscillating circuit of the terminal while no transponder is present in its field and a value of this same current with the second value of the resistive load.

8. The method of claim 6, wherein, in the absence of a determination that the terminal is authentic, said terminal sends incorrect data.

9. An electromagnetic transponder comprising:

an oscillating circuit upstream of a rectifying circuit capable of providing a D.C. voltage when the transponder is present in a magnetic field of a terminal; and

at least one processing unit capable of implementing the method of claim 1.

10. The method of claim 1, wherein determining the authenticity of the terminal comprises verifying that the terminal is inauthentic.

11. The method of claim 1, wherein determining the authenticity of the terminal comprises verifying that the terminal is authentic.

12. The method of claim 1, wherein the first data correspond to a ratio of first and second levels of the current in the oscillating circuit of the terminal, the first level corresponding to the current when no transponder is within a range of the magnetic field of the terminal, the second level corresponding to the current when the transponder is within the range of the magnetic field and the resistive load of the transponder corresponds to said first resistive load value.

13. The method of claim 6, wherein determining the authenticity of the transponder comprises verifying that the transponder is inauthentic.

14. The method of claim 6, wherein determining the authenticity of the transponder comprises verifying that the transponder is authentic.

15. The method of claim 6, wherein the third and fourth data are ratios of first and second levels of the current in the oscillating circuit of the terminal, the first level corresponding to the current when no transponder is within a range of the magnetic field of the terminal, the second level corresponding to the current when the transponder is within the range of the magnetic field and the resistive load of the transponder corresponds to said first resistive load value.

16. A transponder comprising:

an oscillator configured to provide a signal in response to a magnetic field of a terminal;

a rectifier configured to rectify a voltage of the signal provided by the oscillator;

one or more circuits configured to form a resistive load on the oscillator; and

a processor configured to determine an authenticity of the terminal based on a result of comparing a first value with a second value,

wherein the first value relates to a current of an oscillating circuit of the terminal,

wherein the second value relates to a level of the voltage of the signal provided by the oscillator,

and wherein the transponder is configured to receive data corresponding to the current of the oscillating circuit from the terminal.

17. The transponder of claim 16, wherein the one or more circuits comprise a switchable resistive element configured to vary the resistive load on the oscillator.

18. The transponder of claim 16, wherein the switchable resistive element is connected to the output terminals of the rectifying circuit.

19. The transponder of claim 16, wherein the switchable resistive element is configured to perform resistive retromodulation.

20. The transponder of claim 16, wherein the first value corresponds to a ratio of first and second levels of the current in the oscillating circuit of the terminal, the first level corresponding to the current when no transponder is within a range of the magnetic field of the terminal, the second level corresponding to the current in the oscillating circuit of the terminal when the transponder is within the range of the magnetic field and the resistive load corresponds to a first resistive load value.

21. The transponder of claim 20, wherein the second value corresponds to a value of the following expression:

22. The transponder of claim 16, wherein the first value corresponds to a value of the following expression:

23. The transponder of claim 22, wherein the second value corresponds to a second level of the voltage of the signal provided by the oscillator for the second resistive load value.

36. The transponder of claim 16, wherein the second value further relates to a second level of the voltage of the signal provided by the oscillator.

37. The transponder of claim 16, wherein the second value further relates to a value of the resistive load.

38. The transponder of claim 16, wherein the second value further relates to a second value of the resistive load.

24. A transponder comprising:

an oscillator configured to provide a signal in response to a magnetic field of a terminal;

a rectifier configured to rectify a voltage of the signal provided by the oscillator;

one or more circuits configured to form a resistive load on the oscillator; and

means for determining an authenticity of the terminal based on a result of comparing a first value with a second value,

wherein the first value relates to a current of an oscillating circuit of the terminal,

wherein the second value relates to a level of the voltage of the signal provided by the oscillator,

and wherein the transponder is configured to receive data corresponding to the current of the oscillating circuit from the terminal.

25. A system comprising:

a transponder including;

an oscillator configured to provide a signal in response to a magnetic field of a terminal,

a rectifier configured to rectify a voltage of the signal provided by the oscillator,

one or more circuits configured to form a resistive load on the oscillator, and

a processor configured to determine an authenticity of the terminal based on a result of comparing a first value with a second value; and

a terminal configured to generate a magnetic field for the transponder,

wherein the first value relates to a current of an oscillating circuit of the terminal,

wherein the second value relates to a level of the voltage of the signal provided by the oscillator,

and wherein the transponder is configured to receive data corresponding to the current of the oscillating circuit from the terminal.

26. The system of claim 25, wherein the terminal includes means for regulating a phase of the current of the oscillating circuit of the terminal.

27. The system of claim 26, wherein the means for regulating the phase of the current are configured to maintain a constant phase relationship between the current and a reference signal.

28. The system of claim 26, wherein the means for regulating the phase of the current are configured to regulate the phase of the current such that an imaginary part of an apparent impedance of the oscillating circuit is zero.

29. The system of claim 26, wherein the means form regulating the phase of the current comprise means for varying a capacitance of the oscillating circuit and means for detecting a value of the current.

30. The system of claim 25, wherein the terminal includes:

a variable capacitor;

a control circuit configured to regulate a phase of the current of the oscillating circuit of the terminal by controlling a capacitance of the variable capacitor,

wherein controlling the capacitance of the variable capacitor includes;

detecting a phase interval between the current of the oscillating circuit and a reference signal, and

adjusting the capacitance of the variable capacitor so as to reduce the phase interval.

31. The system of claim 30, wherein the control circuit is configured to maintain a constant phase relationship between the current and a reference signal.

32. The system of claim 30, wherein the control circuit is configured to regulate the phase of the current such that an imaginary part of an apparent impedance of the oscillating circuit is zero.

33. The system of claim 30, wherein the control circuit comprises a current measurement element.

34. The system of claim 25, wherein the terminal is further configured to measure the current of the oscillating circuit and to send data to the transponder regarding the current of the oscillating circuit when the transponder is within range of the magnetic field and the resistive load of the transponder corresponds to a first resistive load value.

35. The system of claim 34, wherein the terminal is further configured to receive data from the transponder regarding the current of the oscillating circuit when the transponder is within range of the magnetic field and the resistive load of the transponder corresponds to a second resistive load value.