Integrated circuit and method for challenge-response physically unclonable function

1. An integrated circuit for a challenge-response physically unclonable function (PUF), the integrated circuit comprising:

a PUF block configured to output an internal response having n bits corresponding to a challenge that requests a response, where n is an integer greater than 1;

a response generator configured to calculate a Hamming weight of the internal response and output the response by comparing the Hamming weight with at least one reference defined based on n/2; and

wherein the response generator is configured to generate a pulse sequence by serializing the internal response and to calculate the Hamming weight by counting the pulse sequence.

2. The integrated circuit of claim 1 , wherein

the response generator is configured to output a first value when the Hamming weight is equal to or greater than n/2 and output a second value different from the first value when the Hamming weight is less than n/2.

3. The integrated circuit of claim 1 , wherein

the response generator is configured to output a first value when the Hamming weight is less than or equal to a first reference, which is less than n/2, and output a second value different from the first value when the Hamming weight is equal to or greater than a second reference that is greater than n/2.

4. The integrated circuit of claim 3 , wherein

the response generator is configured to output the response independently from the internal response when the Hamming weight is between the first reference and the second reference.

5. The integrated circuit of claim 1 , further comprising

an internal challenge generator configured to generate an internal challenge from the challenge based on a non-linear function, and

wherein the PUF block is configured to output the internal response based on the internal challenge.

6. The integrated circuit of claim 5 , wherein

the PUF block comprises:

n PUF source circuits each configured to generate a bit signal of a unique value;

a non-inverting circuit configured to output n/2 bits of the internal response by performing a non-inverting function on n/2 bit signals from among n bit signals dependent on bit signals of the n PUF source circuits; and

an inverting circuit configured to output other n/2 bits of the internal response by inverting other n/2 bit signals from among the n bit signals dependent on the bit signals of the PUF source circuits.

7. The integrated circuit of claim 1 , wherein the PUF block comprises a plurality of logic gates and is configured to generate the internal response based on threshold levels of the plurality of logic gates.

8. The integrated circuit of claim 1 , wherein the response generator comprises an asynchronous counter configured to count the pulse sequence.

9. The integrated circuit of claim 1 , further comprising

a first interface circuit configured to output the internal response to outside of the integrated circuit, and

the first interface circuit is configured to be disabled after an enrollment phase is completed.

10. The integrated circuit of claim 1 , further comprising

a second interface circuit configured to output the Hamming weight to outside of the integrated circuit, and

the second interface circuit is configured to be disabled after an enrollment phase is completed.

11. An integrated circuit for a challenge-response physically unclonable function (PUF), the integrated circuit comprising:

a PUF block configured to output an internal response that has n bits and varies according to a challenge that requests a response, where n is an integer greater than 1;

a response generator configured to output the response based on the internal response by counting a bit unit which has a particular value corresponding to at least one bit and comparing a result of the counting with at least one reference defined based on n/2; and

wherein the response generator comprises: a serializer configured to generate a pulse sequence by serializing the internal response; a counter configured to calculate Hamming weight by counting the pulse sequence; and a comparator configured to compare an output signal of the counter with the at least one reference.

12. The integrated circuit of claim 11 , wherein

the response generator is configured to output a first value when the result of the counting is equal to or greater than a probabilistic expected value of the particular value and output a second value different from the first value when the result of the counting is less than the probabilistic expected value.

13. The integrated circuit of claim 11 , wherein

the response generator is configured to output a first value when the a result of the counting is less than or equal to a first reference that is less than a probabilistic expected value of the particular value and output a second value different from the first value when a Hamming weight is equal to or greater than a second reference that is greater than the probabilistic expected value.

14. The integrated circuit of claim 13 , wherein the response generator is configured to independently output the response from the internal response when the result of the counting is between the first reference and the second reference.

15. The integrated circuit of claim 11 , further comprising

an internal challenge generator configured to generate an internal challenge from the challenge based on a non-linear function, and

the PUF block is configured to output the internal response based on the internal challenge.

16. The integrated circuit of claim 13 , wherein the PUF block comprises n PUF source circuits each configured to generate a bit signal of a unique value that varies according to the internal challenge.

17. The integrated circuit of claim 11 , wherein the counter includes an asynchronous counter configured to respond to the pulse sequence.

18. A challenge-response authentication method using an integrated circuit comprising a physically unclonable function (PUF), the challenge-response authentication method comprising:

generating a first challenge, providing the first challenge to the integrated circuit;

obtaining, from the integrated circuit, a first response corresponding to the first challenge; and

evaluating the first response based on a first Hamming weight of an n-bit first internal response generated by the integrated circuit in response to the first challenge, wherein the evaluating the first response comprises comparing the first Hamming weight with at least one reference defined based on n/a; and

wherein generating a pulse sequence by serializing the internal response and to calculate the Hamming weight by counting the pulse sequence.