An electronic system for generating secret information comprising a Physically Unclonable Function, PUF, circuit, the PUF being configured to provide a difference between two values of a physical variable of the PUF in response to a challenge applied to the PUF, wherein the system is configured to apply a set of challenges during an enrolment phase, and measure the physical variable difference provided by the PUF, in response to each challenge, the system comprising: - A helper data generator configured to generate a helper data comprising a set of bits, a bit of the helper data being generated in association with each applied challenge, said helper data generator being configured to generate each helper data bit from the physical variable difference provided by the PUF in response to the application of the associated challenge, the system further comprising a secret information generator for extracting secret information from said helper data, and wherein the helper data generator is configured to select one of at least two bit extraction functions, depending on the value of the physical variable difference, to generate each helper data bit, during the enrolment phase, said at least two bit extraction functions comprising a first bit extraction function and a second bit extraction function, each bit extraction function being configured to return a bit value depending on a condition related to the value of the physical variable difference with respect to at least one reliability threshold, the condition of the first bit extraction function being different from the condition of the second bit extraction function. - A helper data generator configured to generate a helper data comprising a set of bits, a bit of the helper data being generated in association with each applied challenge, said helper data generator being configured to generate each helper data bit from the physical variable difference provided by the PUF in response to the application of the associated challenge, the system further comprising a secret information generator for extracting secret information from said helper data, and wherein the helper data generator is configured to select one of at least two bit extraction functions, depending on the value of the physical variable difference, to generate each helper data bit, during the enrolment phase, said at least two bit extraction functions comprising a first bit extraction function and a second bit extraction function, each bit extraction function being configured to return a bit value depending on a condition related to the value of the physical variable difference with respect to at least one reliability threshold, the condition of the first bit extraction function being different from the condition of the second bit extraction function. the system further comprising a secret information generator for extracting secret information from said helper data, and wherein the helper data generator is configured to select one of at least two bit extraction functions, depending on the value of the physical variable difference, to generate each helper data bit, during the enrolment phase, said at least two bit extraction functions comprising a first bit extraction function and a second bit extraction function, each bit extraction function being configured to return a bit value depending on a condition related to the value of the physical variable difference with respect to at least one reliability threshold, the condition of the first bit extraction function being different from the condition of the second bit extraction function. <EOS>