Authentication of a terminal by an electromagnetic transponder

• US 8,482,388 B2
• Filed: 06/15/2010
• Issued: 07/09/2013
• 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): Lee, Benjamin C
• Assistant Examiner(s): CARLSON, ADAM C
• Application Number:
  US12/815,798
• Publication Number:
  US 20100328046A1
• Time in Patent Office: 1,120 Days
• Field of Search: 340 101- 104, 3405721-5729
• US Class Current: 340/10.4
• CPC Class Codes: G05B 1/01 electric
• 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
• CPC Class Codes: G06K 7/10108 interrogating only those RFIDs that fulfill a predetermined requirement, e.g. selecting all RFIDs having the same speed and moving in a cloud like fashion, e.g. on the same train; interrogating only RFIDs having a certain predetermined temperature, e.g. in the same fridge, another possibility being the active ignoring of a group of tags that fulfill a predetermined requirement, equivalent to the Boolean NOT operation
• CPC Class Codes: G08B 21/0275 Electronic Article Surveillance [EAS] tag technology used for parent or child unit, e.g. same transmission technology, magnetic tag, RF tag, RFID

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 at least one quantity depending on the coupling between the transponder and the terminal is compared with at least one reference 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, comprising:

obtaining at least one quantity, the at least one quantity depending on a coupling between the transponder and the terminal;

comparing the at least one quantity with at least one reference value; and

determining an authenticity of the terminal based on a result of the comparing,

wherein;

obtaining the at least one quantity comprises measuring a first quantity corresponding to a level of said D.C. voltage; and

comparing the at least one quantity comprises comparing the first quantity with a first reference value, the first reference value depending on a level of said voltage in a condition of optimum coupling between the transponder and the terminal.

2. The method of claim 1, wherein said first reference value associated with the optimum coupling condition is deduced from a training phase.

3. The method of claim 1, wherein:

obtaining the at least one quantity comprises measuring and storing a first quantity corresponding to a level of said D.C. voltage for a first value of a resistive load formed by circuits of the transponder on the oscillating circuit;

obtaining the at least one quantity further comprises measuring and storing a second quantity corresponding to a level of said D.C. voltage for a second value of the resistive load on the oscillating circuit; and

comparing the at least one quantity comprises comparing a ratio between the first and second quantities with one or several reference values.

4. The method of claim 3, wherein said one or several reference values depend on the respective resistive load values.

5. The method of claim 3, further comprising varying the resistive load between the first and second values by modifying the consumption of processing circuits comprised by the transponder.

6. The method of claim 3, further comprising varying the resistive load between the first and second values by switching a resistive retromodulation element comprised by the transponder.

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

8. 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 the magnetic field of a terminal; and

at least one processor capable of implementing the method of claim 1.

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

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

11. A method comprising:

obtaining one or more quantities associated with a circuit of a transponder, the one or more quantities depending on a load formed by one or more circuits of the transponder;

comparing the one or more quantities with one or more reference values; and

determining an authenticity of a terminal based on one or more results of the comparing,

wherein obtaining the one or more quantities comprises measuring a first level of a voltage for a first configuration of the load, and

wherein comparing the one or more quantities comprises comparing the first level of the voltage to a predetermined level of the voltage for the first configuration of the load and for an optimum coupling factor between the transponder and the terminal.

12. The method of claim 11, wherein:

determining the authenticity of the terminal comprises verifying whether the terminal is authentic or inauthentic; and

the method further comprises communicating with the terminal if the terminal is verified to be authentic, or performing error processing if the terminal is verified to be inauthentic.

13. The method of claim 12, wherein:

the transponder comprises an oscillating circuit from which a D.C. voltage is generated, and a processor; and

the obtaining, comparing, and verifying are performed by the processor.

14. The method of claim 11, wherein obtaining the one or more quantities further comprises measuring a second level of the voltage for a second configuration of the load.

15. The method of claim 14, wherein comparing the one or more quantities comprises comparing a ratio of the second and first levels of the voltage to a predetermined value, wherein the predetermined value is 1 and/or a ratio of values associated with the second and first configurations of the load.

16. The method of claim 14, wherein comparing the one or more quantities comprises comparing the first level of the voltage to a value of the following expression:

17. The method of claim 14, wherein comparing the one or more quantities comprises comparing the first level of the voltage to a value of the following expression:

28. The method of claim 11, wherein a first of the one or more quantities depends on a coupling between the transponder and the terminal.

18. An electromagnetic 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 a terminal based on a result of comparing at least one quantity with at least one reference value, the at least one quantity depending on a coupling between the transponder and the terminal,

wherein the at least one quantity comprises a first measured level of a voltage of the signal provided by the oscillator, and

wherein comparing the at least one quantity with the at least one reference value comprises comparing the first measured level of the voltage with a first reference value, the first reference value depending on a level of said voltage in a condition of optimum coupling between the transponder and a terminal.

19. The electromagnetic transponder of claim 18, wherein the one or more circuits comprise a switchable resistive element configured to vary the resistive load on the oscillator.

20. The electromagnetic transponder of claim 19, wherein the switchable resistive element is connected to the output terminals of the rectifier.

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

29. The electromagnetic transponder of claim 18, wherein the at least one quantity depends on the resistive load.

22. An electromagnetic 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 a terminal based on a result of comparing at least one quantity with at least one reference value, the at least one quantity depending on the resistive load on the oscillator,

wherein the at least one quantity comprises a first measured level of a voltage of the signal provided by the oscillator for a first configuration of the resistive load, and

wherein comparing the at least one quantity with the at least one reference value comprises comparing the first measured level of the voltage with a predetermined level of the voltage for the first configuration of the load and for an optimum coupling factor between the transponder and a terminal.

30. The electromagnetic transponder of claim 22, wherein the at least one quantity depends on a coupling between the transponder and the terminal.

23. An electronic system, comprising:

a terminal comprising a first oscillator for generating a magnetic field; and

an electromagnetic transponder comprising;

a second oscillator configured to provide a signal in response to the magnetic field,

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

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

a processor configured to determine an authenticity of the terminal based on a result of comparing at least one quantity with at least one reference value, the at least one quantity depending on a coupling between the transponder and the terminal,

wherein the at least one quantity comprises a first measured level of a voltage of the signal provided by the second oscillator, and

wherein comparing the at least one quantity with the at least one reference value comprises comparing the first measured level of the voltage with a first reference value, the first reference value depending on a level of said voltage in a condition of optimum coupling between the transponder and a terminal.

24. The system of claim 23, wherein the terminal includes means for regulating a phase of a current of the oscillating circuit of the terminal.

25. The system of claim 24, 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.

26. The system of claim 24, 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.

27. The system of claim 23, wherein the at least one quantity depends on the resistive load.