Systems and methods for classifying PUF signature modules of integrated circuits

1. A method of determining a reliability of a physically unclonable function (PUF) cell of a device, comprising:

providing one or more activation signals to a PUF cell under each of a plurality of conditions, wherein, under at least one of the plurality of conditions, providing the one or more activation signals comprises providing a first signal to a first branch of the PUF cell and a second signal in series with the first signal to a second branch of the PUF cell;

determining a PUF cell output provided by the PUF cell under each of the plurality of conditions;

determining a number of times that the PUF cell outputs of the PUF cell are consistent; and

determining a device classification value, based on a comparison between the determined number of times that the PUF cell outputs of the PUF cell are consistent and a threshold number or range, for a plurality of PUF cells.

2. The method of claim 1 , wherein, under at least one of the plurality of conditions, providing the one or more activation signals and determining the PUF cell output, comprises:

providing a third signal to the first branch of the PUF cell and a fourth signal to the second branch of the PUF cell, the third and fourth signals being provided in synchronization;

determining a first PUF cell output of the PUF cell produced by the first signal and the second signal; and

determining a second PUF cell an output of the PUF cell produced by the third signal and the fourth signal.

3. The method of claim 1 , further comprising:

determining that the PUF cell is unusable when the determined number of times that the PUF cell outputs are consistent is fewer than a minimum threshold number.

4. The method of claim 3 , wherein the minimum threshold number is based on a number of determined PUF cell outputs of the PUF cell.

5. The method of claim 1 , further comprising:

determining that the PUF cell is usable for a first class of operation when the determined number of times that the PUF cell outputs are consistent is at least a first threshold number.

6. The method of claim 5 , wherein the first threshold number is equal to a number of times the PUF cell outputs are determined.

7. The method of claim 5 , further comprising:

determining that the PUF cell is usable for a second class of operation when the determined number of times that the PUF cell outputs are consistent is at least a second threshold number but fewer than the first threshold number.

8. The method of claim 5 , wherein the device classification value is determined based on a number of PUF cells determined to be usable for the first class of operation.

9. The method of claim 7 , wherein the device classification value is determined based on a number of PUF cells determined to be usable for the second class of operation.

10. The method of claim 1 , further comprising:

determining that the PUF cell is unusable when the determined number of times that the PUF cell outputs are consistent is fewer than a threshold number; and

storing a mask in a computer-readable memory that identifies unusable PUF cells of the device.

11. The method of claim 10 , wherein the threshold number is based on the device classification value.

12. The method of claim 10 , further comprising:

determining a device signature based on usable PUF cells using the mask.

13. The method of claim 12 , further comprising utilizing the device signature by:

transmitting the device signature from the device to identify the device,

signing a communication from the device using the device signature, or

encrypting a communication from the device using the device signature.

14. The method of claim 13 , further comprising appending one or more error correction bits to the device signature prior to utilizing the device signature.

15. A device configured to provide a physically unclonable function (PUF) value, comprising:

a control signal generator configured to provide one or more activation signals to a PUF cell under each of a plurality of conditions, wherein, under at least one of the plurality of conditions, the control signal generator is configured to provide the one or more activation signals by providing a first signal to a first branch of the PUF cell and a second signal in series with the first signal to a second branch of the PUF cell; and

a PUF strength analyzer configured to determine a PUF cell output provided by the PUF cell under each of the plurality of conditions, to determine a number of times that the PUF cell outputs of the PUF cell are consistent, and to determine a device classification value based on a comparison between the determined number of times that the PUF cell outputs of the PUF cell are consistent and a threshold number or range, for a plurality of PUF cells.

16. The device of claim 15 , wherein, under at least one of the plurality of conditions, the control signal generator is configured to provide the one or more activation signals by:

providing a third signal to the first branch of the PUF cell and a fourth signal to the second branch of the PUF cell in synchronization.

17. The device of claim 16 , wherein the PUF strength analyzer is configured to determine the PUF cell output by:

determining a first PUF cell output of the PUF cell produced by the first signal and the second signal; and

determining a second PUF cell output of the PUF cell produced by the third signal and the fourth signal.

18. The device of claim 15 , wherein the PUF strength analyzer is further configured to determine that the PUF cell is unusable when the number of times that the PUF cell outputs are consistent is fewer than a minimum threshold number.

19. The device of claim 18 , wherein the minimum threshold number is based on a number of determined PUF cell outputs of the PUF cell.

20. A non-transitory computer-readable medium encoded with instructions for commanding one or more data processors to execute steps of a method of determining a reliability of a physically unclonable function (PUF) cell of a device, the steps comprising:

providing one or more activation signals to a PUF cell under each of a plurality of conditions, wherein, under at least one of the plurality of conditions, providing the one or more activation signals comprises providing a first signal to a first branch of the PUF cell and a second signal in series with the first signal to a second branch of the PUF cell;

determining a PUF cell output provided by the PUF cell under each of the plurality of conditions;

determining a number of times the PUF cell outputs of the PUF cell are consistent; and

determining a device classification value, based on a comparison between the determined number of times that the PUF cell outputs of the PUF cell are consistent and a threshold number or range, for a plurality of PUF cells.