Method of implementing a physical unclonable function

1. A method of identifying primitives for implementing a physical unclonable function providing a response representative of a device,

wherein said device comprises a plurality of primitives coupled in pairs (P 1 , . . . , P 6 ), wherein the primitives are electronic units,

and wherein said primitives are configured for being one-time programmable by changing their state from a not-programmed state to a programmed state through application of a burning energy to said primitives, the method comprising:

selecting (S 1 ) a subset of the pairs,

assessing (S 2 ) a difference between electrical characteristics values provided by primitives belonging to each pair of said subset,

qualifying (S 3 ) all pairs of primitives for which the assessed difference is higher than a reference threshold, and

identifying (S 4 ) said qualified pairs of primitives, said identifying step comprising a step of programming (S 4 ) at least one primitive of each pair of primitives for which the assessed difference is lower than said reference threshold, by applying a burning energy to said at least one primitive so as to differentiate qualified pairs of primitives from those that are not qualified.

2. The method according to claim 1 , wherein the reference threshold is adjusted in function of a targeted ratio of qualified pairs to all pairs of the subset.

3. The method according to claim 1 , wherein, at least one primitive of the device being a transistor, the step of programming at least one primitive comprises applying a voltage on a gate of at least one transistor.

4. The method according to claim 1 , wherein both primitives of each pair of primitives for which the assessed difference is lower than said reference threshold are programmed.

5. A method for executing a physical unclonable function of a device,

wherein said device comprises a plurality of primitives coupled in pairs (P 1 , . . . , P 6 ), wherein the primitives are electronic units,

wherein said primitives are configured for being one-time programmable by changing their state from a not-programmed state to a programmed state through application of a burning energy to said primitives, and some of said pairs of primitives have been identified as qualified by

selecting (Si) a subset ( 20 ) of the pairs,

assessing (S 2 ) a difference between electrical characteristics values provided by primitives belonging to each pair of said subset,

qualifying (S 3 ) all pairs of primitives for which the assessed difference is higher than a reference threshold, and

identifying (S 4 ) said qualified pairs of primitives, said identifying step comprising a step of programming (S 41 ) at least one primitive of each pair of primitives for which the assessed difference is lower than said reference threshold, by applying a burning energy to said at least one primitive so as to differentiate qualified pairs of primitives from those that are not qualified,

wherein the method comprises:

reading (EI) a state of all primitives of said device,

based on said read states, differentiating (E 2 ) the qualified pairs of primitives identified according to the method of claim 1 ,

generating (E 3 ) a physical unclonable function response only from primitives belonging to said qualified pairs.

6. The method for executing a physical unclonable function of a device of claim 5 wherein a programming step has been performed according to claim 3 , and wherein the step of reading a state of a primitive of said device (E 1 ) comprises when said primitive is a transistor:

injecting a current through a gate of said transistor,

comparing a voltage of said gate to a voltage reference,

based on said comparison, determining the state of said primitive.

7. A device comprising a plurality of primitives coupled in pairs (P 1 , . . . , P 6 ), wherein the primitives are electronic units,

wherein said primitives are configured for being one-time programmable by changing their state from a not-programmed state to a programmed state through application of a burning energy to said, primitives, wherein the device comprises:

a selector configured to select a subset of the pairs of primitives,

a comparator configured to assess a difference between electrical characteristics values provided by primitives belonging to each pair of the subset, and configured to qualify all pairs of primitives for which the assessed difference is higher than a reference threshold, said qualified pairs corresponding to primitives selected for implementing a physical unclonable function providing a response representative of the device,

and a programming circuit configured to program at least one primitive of each pair of primitives for which the assessed difference is lower than said reference threshold, by applying a burning energy to said at least one primitive so as to differentiate qualified pairs of primitives from those that are not qualified.

8. The device according to claim 7 , wherein the device comprises a generator configured to generate a PUF response by running the physical unclonable function, the generator being configured to generate the response from only the qualified pairs.

9. The device according to claim 7 , wherein the device is a chip or a system-on-a-chip.

10. The device according to claim 7 , wherein the device is a printed circuit board and primitives are electronic components.

11. The device according to claim 10 , wherein at least one primitive of the device is a transistor.

12. The device according to claim 7 , wherein the device is a RFID tag.