Systems and methods for classifying puf signature modules of integrated circuits
View Patent ↗Systems and method are provided for determining a reliability of a physically unclonable function (PUF) cell of a device. One or more activation signals are provided to a PUF cell under a plurality of conditions. A PUF cell output provided by the PUF cell under each of the plurality of conditions is determined. A determination is made of a number of times the PUF cell output of the PUF cell is consistent. And a device classification value is determined based on the determined number of times for a plurality of PUF cells.
1. A method comprising:
providing signals to a cell under a plurality of conditions;
under a first condition of the plurality of conditions, providing a first signal to a first wordline connected to a gate terminal of a first transistor within a first branch of the cell and a second signal to a second wordline connected to a gate terminal of a second transistor within a second branch of the cell;
determining a number of times that cell outputs of the cell are consistent under the plurality of conditions; and
determining a device classification value, based on a comparison between the determined number of times and a threshold number or range, for a plurality of cells.
2. The method of claim 1 , further comprising:
under a second condition of the plurality of conditions, providing a third signal to the first branch and a fourth signal to the second branch, the third and fourth signals being provided in synchronization;
determining a first cell output of the cell produced by the first signal and the second signal; and
determining a second cell output of the cell produced by the third signal and the fourth signal.
3. The method of claim 1 , further comprising determining that the cell is unusable when the number of times that cell outputs of the cell 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 cell outputs of the cell.
5. The method of claim 1 , further comprising determining that the cell is usable for a first class of operation when the number of times that cell outputs of the cell 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 cell outputs of the cell.
7. The method of claim 5 , further comprising determining that the cell is usable for a second class of operation when the number of times that cell outputs of the cell are consistent is at least a second threshold number but fewer than the first threshold number.
8. The method of claim 7 , wherein the device classification value is determined based on a number of cells determined to be usable for the second class of operation.
9. The method of claim 5 , wherein the device classification value is determined based on a number of cells determined to be usable for the first class of operation.
10. The method of claim 1 , further comprising:
determining that the cell is unusable when the number of times that cell outputs of the cell are consistent is fewer than a threshold number; and
storing a mask in a computer-readable memory that identifies unusable cells.
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 cells using the mask.
13. The method of claim 12 , further comprising utilizing the device signature by:
transmitting the device signature from a 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 reconstruct the device signature prior to utilizing the device signature.
15. A device comprising:
a plurality of cells, wherein, under a first condition of a plurality of conditions, a cell is configured to receive a first signal from a first wordline at a gate terminal of a first transistor of a first branch of the cell and a second signal from a second wordline at a gate terminal of a second transistor of a second branch of the cell; and
an analyzer configured to determine a device classification value, wherein the analyzer is configured to determine a number of times that cell outputs of the cell are consistent under the plurality of conditions, and the device classification value is determined based on a comparison between the determined number of times and a threshold number or range, for the plurality of cells.
16. The device of claim 15 , wherein, under a second condition of the plurality of conditions, the first branch is configured to receive a third signal and the second branch is configured to receive a fourth signal in synchronization with the third signal.
17. The device of claim 16 , wherein the analyzer is further configured to determine a first cell output of the cell produced by the first signal and the second signal and a second cell output of the cell produced by the third signal and the fourth signal.
18. The device of claim 15 , wherein the analyzer is further configured to determine that the cell is unusable when the number of times that cell outputs of the cell 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 cell outputs of the cell.
20. A non-transitory computer-readable medium encoded with instructions for commanding one or more data processors to execute steps of a method, the steps comprising:
providing signals to a cell under a plurality of conditions;
under a first condition of the plurality of conditions, providing a first signal to a first wordline connected to a gate terminal of a first transistor of the cell and a second signal to a second wordline connected to a gate terminal of a second transistor of the cell;
determining a number of times that cell outputs of the cell are consistent under the plurality of conditions; and
determining a device classification value, based on a comparison between the determined number of times and a threshold number or range, for a plurality of cells.