Providing a specific output in response to a specific input

A device provides a specific output 40 in response to a specific input, the device comprising a physical unclonable function (PUF) arranged to be challenged with the specific input and to provide a unique output in response, and the device being arranged to facilitate the detection of the unique output by a detection arrangement. The device further comprises an offset arrangement, configured to receive the unique output 44 and apply a specific offset 46 to it, in order to provide the specific output 40. The offset is fixed and so the specific output is only achieved when the unique output is detected. The offset arrangement is programmed in advance with reference to the specific output. The detection arrangement may be part of the device or external. The PFU may comprise a structure that exhibits quantum mechanical confinement and provides a unique output response linked to the atomic makeup of the structure. The detection may involve an electrical measurement of an output of the structure, the electrical output involving tunnelling. An electrical circuit may be enabled or disabled depending on whether the device output is the specific output.