METHOD FOR ENROLLING A PHYSICALLY UNCLONABLE FUNCTION, PUF, CIRCUIT FOR CRYPTOGRAPHIC APPLICATIONS

Method for enrolling a Physically Unclonable Function, PUF, circuit for cryptographic applications, comprising: providing a plurality of modules (11), each module (11) comprising at least three embedded PUF cells (x, y, z), each cell (x, y, z) being configured to give an output upon application of an input. For each module (11), the following operations are executed: defining a reference temperature; for each cell pair (x-y, x-z, y-z) belonging to said module (11), initializing a respective helper bit (HDA, HDB, HDC) to a default value; bringing said module (11) to said reference temperature; applying to each cell (x, y, z) the respective input; identifying, among said cell pairs (x-y, x-z, y-z), a first cell pair having the highest resistive ratio; defining the output of the module (11) as a function of the output of the cells of the first pair. The temperature of said modules is then modified within a range of interest. If, as the temperature changes, the first cell pair is still the one with the highest resistive ratio, then the helper bits (HDA, HDB, HDC) are left unchanged. If, as the temperature changes, a second cell pair, other than said first cell pair, becomes the one with the highest resistive ratio, then the following operations are executed: determining a next output on the basis of the outputs of the cells of the second pair; if the next output is equal to the output of the module, then the helper bits (HDA, HDB, HDC) are left unchanged; if the next output is different from the output of the module, then the value of the helper bit associated with said second cell pair is modified. A helper bit (HDA, HDB, HDC) vector is finally outputted.