Authenticatable device with reconfigurable physical unclonable functions

Patent metadata

Field	Value
Publication number	US-9806718-B2
Application number	US-201615176766-A
Country	US
Kind code	B2
Filing date	Jun 8, 2016
Priority date	May 5, 2014
Publication date	Oct 31, 2017
Grant date	Oct 31, 2017

Abstract

An authenticatable device according to one embodiment includes a reconfigurable physical unclonable function (‘RPUF’) used with one parameter to recover sensitive values (e.g., a secret or a share of a secret) and a different parameter to encode and store values (e.g., challenge-helper pairs) correlated to the sensitive values. In another embodiment, a pair of RPUFs is used instead of a single PUF, with one RPUF used to recover sensitive values and the other RPUF used to encode and store correlated values. In still another embodiment, the desired expiration of values can be enforced by employing redundant RPUFs; when the device is powered on, one (or more than one, but less than all) of the RPUFs is selected and transitioned to a new configuration, invalidating any correlated values previously constructed using the old configuration, and the RPUF that was not reconfigured is used to recover the sensitive value(s) using the remaining correlated value(s).

First claim

What is claimed is:

1. An authenticatable device comprising:
at least a first and second reconfigurable physical unclonable function (‘RPUF’) circuits constructed to generate, in response to input of a challenge, an output value that is characteristic to the RPUF circuit, a configuration of the RPUF circuit, and the challenge;
a memory;
one or more processors configured to:
cause an RPUF circuit to be reconfigured responsive to powering up the authenticatable device;
cause a challenge to be issued to the RPUF circuits;
store in the memory a putative value or values that corresponds to a respective RPUF circuit's response, wherein at least the putative value or values corresponding to the RPUF circuit that was not reconfigured in response to the power event is correlated to a secret or a share of a secret;
responsive to a request to perform a cryptographic operation, cause a challenge to be issued at least to the RPUF circuit that was not reconfigured generate an executable version of the secret or the share of a secret using the RPUF circuit's response with the putative correlated value or values that was stored for that RPUF circuit.

2. The authenticatable device of claim 1 , wherein the one or more processors is configured to cause a challenge to be issued responsive to the request to perform the cryptographic operation only to the RPUF circuit that was not reconfigured to cause a challenge to be issued only to the RPUF circuit that was not reconfigured.

3. The authenticatable device of claim 1 , wherein the secret or a share of a secret is a share of a secret, and the one or more computing processors is further reconfigured to cause a challenge to be issued, store in the memory the putative value or values, and responsive to the request to perform the cryptographic operation, cause a challenge to be issued as many times as there are shares of the secret.

4. The authenticatable device of claim 3 , wherein the one or more computing processors is further configured to periodically refresh the shares of the secret.

5. The authenticatable device of claim 1 , wherein each RPUF circuit is irreversibly reconfigurable.

6. The authenticatable device of claim 5 , wherein each RPUF circuit is physically reconfigurable.

7. The authenticatable device of claim 1 , wherein the first and second RPUF circuits are logically reconfigurable.

8. The authenticatable device of claim 7 , further comprising a random number generator wherein the random number generator is a true random number generator.

9. The authenticatable device of claim 1 , wherein the memory is non-volatile.

10. The authenticatable device of claim 9 , wherein each putative correlated value or values is a challenge-helper pair.

11. The authenticatable device of claim 1 , further comprising a random number generator, wherein the processor is further configured to store in a volatile memory a random number for use in selecting which RPUF circuit to reconfigure.

12. The authenticatable device of claim 1 , further comprising a backup RPUF circuit for each RPUF circuit.

13. The authenticatable device of claim 12 , further comprising a non-volatile memory, wherein the one or more computing processors is configured to store a public key for the device in the non-volatile memory and to, upon power-up, generate a putative public key using the memory and the RPUF circuit not reconfigured, and engage the backup RPUF circuits if the putative public key thus generated does not match the device's stored public key.

14. The authenticatable device of claim 1 , wherein the executable version of the secret or the share of a secret comprises the secret or the share of the secret or a combination of threshold operations on the secret or the share of the secret.

15. A computer implemented method for authenticating a device with reconfigurable physical unclonable function (‘RPUF’) circuits, the method comprising:
reconfiguring, by at least one processor, an RPUF circuit responsive to powering up the device;
issuing, the at least one processor, to a first and second RPUF circuits, wherein the RPUF circuits are constructed to generate, in response to input of a challenge, an output value that is characteristic to the RPUF circuit, a configuration of the RPUF circuit, and the challenge;
storing, by the at least one processor, in a memory a putative value or values that corresponds to a respective RPUF circuit's response, wherein at least the putative value or values corresponding to the RPUF circuit that was not reconfigured in response to the power event is correlated to a secret or a share of a secret;
responsive to receiving a request to perform a cryptographic operation, causing, by the at least one processor, a challenge to be issued at least to the RPUF circuit that was not reconfigured; and
enabling, by the at least one processor, the cryptographic operation associated with the secret or the share of the secret using at least the response generated by the RPUF circuit that was not reconfigured and the putative value or values stored for that RPUF circuit.

16. The method of claim 15 , wherein the secret or the share of a secret is not generated in the memory.

17. The method of claim 15 , further comprising an act of refreshing the shares of the secret.

18. The method of claim 15 , wherein the act of causing, by the at least one processor, the challenge to be issued at least to the RPUF circuit that was not reconfigured, includes only causing the challenged to be issued to the RPUF circuit that was not reconfigured.

19. An authenticatable server comprising:
at least a first and second reconfigurable physical unclonable function (‘RPUF’) circuits constructed to generate, in response to input of a challenge, an output value that is characteristic to the RPUF circuit, a configuration of the RPUF circuit, and the challenge;
a memory;
one or more processors configured to:
cause an RPUF circuit to be reconfigured responsive to powering up the server;
issue a challenge to the RPUF circuits;
store in the memory a putative value or values that corresponds to a respective RPUF circuit's response, wherein at least the putative value or values output by the RPUF circuit that was not reconfigured in response to the event, is correlated to a secret or a share of a secret; and
responsive to a request to perform a cryptographic operation, cause a challenge to at least the RPUF circuit that was not reconfigured, and enable the cryptographic operation associated with the secret or the share of the secret using at

least the response generated by the RPUF circuit that was not reconfigured and the putative value or values stored for that RPUF circuit.

20. The authenticable system of claim 18 , wherein the secret or the share of a secret is not generated in the memory.

Assignees

• Analog Devices Inc

Inventors

• Wallrabenstein John Ross

Classifications

• H04L9/0866

  involving user or device identifiers, e.g. serial number, physical or biometrical information, DNA, hand-signature or measurable physical characteristics · CPC title

• H03K19/17748 Primary

  Structural details of configuration resources · CPC title

• H04L2209/12

  Details relating to cryptographic hardware or logic circuitry · CPC title

• G06F21/44

  Program or device authentication · CPC title

• H04L9/3278

  using physically unclonable functions [PUF] · CPC title