Embodiments of the invention provide an electronic system for generating secret information comprising a Physically Unclonable Function (PUF) circuit, the PUF circuit 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 circuit. 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 comprises: a helper data generator (2) 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, the 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, a secret information generator (3) configured to generate a secret key comprising at least one bit during a usage phase, each bit of the key being generated by applying a challenge among the set of challenges, the secret information generator (3) being configured to determine each bit of the key from the helper data bit corresponding to the applied challenge, and from the physical variable difference provided by the PUF in response to the applied challenge.