Device security with physically unclonable functions

1. A method, comprising:

receiving, with circuitry, first physically unclonable function (PUF) data from a first PUF source of a payment reader, the first PUF data generated by the first PUF source in response to a first challenge;

receiving, with the circuitry, second PUF data from the first PUF source or a second PUF source, the second PUF data generated by the first PUF source or the second PUF source in response to a second challenge;

comparing, with the circuitry, the first PUF data and the second PUF data;

determining, with the circuitry based on the comparing, a degree of randomness of the first PUF source in generating the first PUF data, wherein the determining comprises determining a value indicating the degree of randomness; and

comparing, with the circuitry, a threshold to the value indicating the degree of randomness; and

controlling whether the payment reader uses PUF values from the first PUF source to perform a secure operation for a payment transaction based on the comparing the threshold to the value indicating the degree of randomness that was determined.

2. The method of claim 1 , wherein the second PUF data is received from the first PUF source, and wherein the method further comprises:

transmitting, with the circuitry, the first challenge to the first PUF source; and

transmitting, with the circuitry, the second challenge to the first PUF source,

wherein the first PUF data includes a first PUF value based on the first challenge, and wherein the second PUF data includes a second PUF value based on the second challenge.

3. The method of claim 1 , wherein the second PUF data is generated by the second PUF source.

4. The method of claim 1 , wherein the second PUF data is generated by the first PUF source, and wherein the first challenge and the second challenge are different.

5. A payment reader, comprising:

an interface configured to receive payment data from a payment device;

at least one physically unclonable function (PUF) source for generating a plurality of PUF values; and

circuitry configured to process a payment transaction based on the payment data and to perform a secure operation for the payment transaction, the circuitry configured to compare the plurality of PUF values for determining a degree of randomness of the at least one PUF source in generating the plurality of PUF values, wherein the circuitry is configured to determine a value indicating the degree of randomness, the circuitry is configured to compare a threshold to the value indicating the degree of randomness, and the circuitry further configured to determine, based on the comparing the threshold to the value indicating the degree of randomness that was determined, whether to use PUF values from the at least one PUF source to perform the secure operation.

6. The payment reader of claim 5 , wherein the circuitry is configured to transmit a first challenge and a second challenge to the at least one PUF source, and wherein the plurality of PUF values include a first PUF value based on the first challenge and a second PUF value based on the second challenge.

7. The payment reader of claim 6 , wherein the circuitry is configured to determine the degree of randomness based on a comparison of the first PUF value to the second PUF value.

8. The payment reader of claim 5 , wherein the at least one PUF source comprises a first PUF source and a second PUF source, and wherein the circuitry is configured to determine the degree of randomness based on a comparison of a first PUF value from the first PUF source and a second PUF value from the second PUF source.

9. The payment reader of claim 5 , wherein the at least one PUF source comprises a plurality of memory cells, each of the plurality of memory cells for providing a respective bit for at least one of the plurality of PUF values.

10. The payment reader of claim 5 , wherein the at least one PUF source comprises a plurality of ring oscillators, wherein the circuitry is configured to compare frequencies of the plurality of ring oscillators for determining at least one of the plurality of PUF values.

11. A method, comprising:

receiving, with circuitry, a plurality of physically unclonable function (PUF) values from at least one PUF source of a payment reader;

analyzing, with the circuitry, the plurality of PUF values;

determining, with the circuitry based on the analyzing, a degree of randomness of the at least one PUF source in generating the plurality of PUF values, wherein the determining comprises determining a value indicating the degree of randomness;

comparing, with the circuitry, a threshold to the value indicating the degree of randomness; and

controlling whether the payment reader uses PUF values from the first PUF source to perform a secure operation for a payment transaction based on the comparing the threshold to the value indicating the degree of randomness that was determined.

12. The method of claim 11 , further comprising:

transmitting, with the circuitry, a first challenge to the at least one PUF source;

transmitting, with the circuitry, a second challenge to the at least one PUF source,

wherein the plurality of PUF values include a first PUF value based on the first challenge and a second PUF value based on the second challenge.

13. The method of claim 12 , wherein the analyzing comprises comparing the first PUF value and the second PUF value.

14. The method of claim 11 , wherein the at least one PUF source comprises a first PUF source, and wherein the analyzing comprises comparing a first PUF value from the first PUF source to a second PUF value from a second PUF source.

15. The method of claim 11 , wherein the at least one PUF source comprises a first PUF source and a second PUF source, and wherein the degree of randomness is determined based on a comparison of a first PUF value from the first PUF source and a second PUF value from the second PUF source.

16. The method of claim 11 , wherein the at least one PUF source comprises a plurality of memory cells, and wherein the method comprises providing, by each of the plurality of memory cells, a respective bit for at least one of the plurality of PUF values.

17. The method of claim 11 , wherein the at least one PUF source comprises a plurality of ring oscillators, wherein the method further comprises comparing frequencies of the plurality of ring oscillators, and wherein determining is based on the comparing.