SYSTEM AND METHOD FOR CRYPTOGRAPHIC KEY IDENTIFICATION

• US 20150200775A1
• Filed: 01/09/2015
• Published: 07/16/2015
• Est. Priority Date: 01/10/2014
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Guajardo Merchan, Jorge, Stahl, Heiko, Lewis, Matthew, Schellin, Ralf, Mueller, Andreas
• Granted Patent: US 9,667,419 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 21/73 by creating or determining hardware identification, e.g. serial numbers
• CPC Class Codes: H04L 9/0866 involving user or device identifiers, e.g. serial number, physical or biometrical information, DNA, hand-signature or measurable physical characteristics

Abstract

A method for determining a cyrptographic key for a MEMS device includes identifying physical properties for the device. A feature vector having a plurality of values is determined. Each of the values correspond to different physical properties. The cryptographic key is determined from the feature vector. The cryptographic key can be determined using a fuzzy extractor. The cryptographic key can be determined using different feature vectors corresponding to different channels in a device or different MEMS structures in the device.

Claims

1. A method for deriving a cryptographic key for a MEMS device, comprising:

identifying a plurality of physical properties of the device;

determining a feature vector for the device having a plurality of values, each of the values corresponding to a different physical property from the plurality of physical properties; and

deriving the cryptographic key from the feature vector.

2. The method of claim 1, wherein the plurality of physical properties of the device includes at least one of a resonant frequency, stiffness of a spring constant with reference to the resonant frequency, a raw offset of the device, a capacitance in the device, a release voltage, a difference in two or more snap voltages, an attenuation value of movement of the device, a resistance in the device, an inductance, a movement curve, an inherent circuit interference, a spectrum pattern, and a voltage applied to a test signal.

3. The method of claim 2, further comprising:

obtaining the capacitance by displacing the device.

4. The method of claim 1, wherein the device comprises a first MEMS structure and the plurality of physical properties are properties of the first MEMS structure.

5. The method of claim 4, wherein the device comprises a second MEMS structure and the plurality of physical properties includes a first group of properties corresponding to the first MEMS structure and a second group of properties corresponding to the second MEMS structure.

6. The method of claim 5, further comprising:

determining a first feature vector for the device having a first plurality of first values, each of the first values corresponding to a different physical property from first group of properties;

determining a second feature vector for the device having a second plurality of second values, each of the second values corresponding to a different physical property from second group of properties; and

deriving the cryptographic key from the first feature vector and the second feature vector.

7. The method of claim 6, wherein the derivation of the cryptographic key further comprises:

providing the first feature vector and the second feature vector to a fuzzy extractor; and

deriving the cryptographic key using the fuzzy extractor.

8. The method of claim 7, further comprising:

identifying the cryptographic key based on a pair-wise comparison of the first feature vector and the second feature vector.

9. The method of claim 6, wherein the derivation of the cryptographic key further comprising:

performing a comparison of the first feature vector and the second feature vector to generate a single bit;

performing an error correction computation of the single bit; and

deriving the cryptographic key based on the single bit.

10. The method of claim 9, wherein the comparison is a pair-wise comparison of the first feature vector and the second feature vector.

11. The method of claim 6, wherein the derivation of the cryptographic key further comprises:

determining a plurality of feature vectors for a portion of channels of the first MEMS structure and the second MEMS structure; and

deriving the cryptographic key from the plurality of feature vectors.

12. The method of claim 11, wherein the portion of channels includes channels configured for security applications.

13. The method of claim 1, wherein the derivation of the cryptographic key further comprises:

deriving the cryptographic key using a fuzzy extractor.

14. The method of claim 13, further comprising:

storing data from the fuzzy extractor in a non-volatile memory.

15. A method for deriving a cryptographic key for a MEMS device, comprising:

identifying a plurality of channels of the device;

identifying a plurality of properties for a portion of the plurality of channels;

determining a plurality of feature vectors, each of the feature vectors corresponding to a different channel from the portion of the plurality of channels and having a plurality of values, each of the values corresponding to a different physical property from the corresponding channel; and

deriving the cryptographic key from the plurality of feature vectors.

16. The method of claim 15, wherein the determining a plurality of feature vectors further comprises:

determining a plurality of feature vectors, each of the feature vectors corresponding to a different channel from the portion of the plurality of channels and formed by concatenating the plurality of physical properties for the corresponding channel; and

deriving the cryptographic key from the plurality of feature vectors.

17. The method of claim 15, wherein the portion of the plurality of channels includes channels configured for security key applications.

18. The method of claim 15, wherein the portion of the plurality of channels includes channels configured for standard device applications.

19. The method of claim 15, wherein the derivation of the cryptographic key further comprises:

deriving the cryptographic key using a fuzzy extractor.

20. The method of claim 19, further comprising:

storing data from the fuzzy extractor in a non-volatile memory.