The present invention relates to a method and a device (11) using a physical token (14), which provides measurable parameters, to derive at least one data set. A plurality of values of one or more of the parameters are measured. From these measured values, a measure of variance is calculated. Quantization intervals into which a measured value is to be quantized are then determined. A possible value of a data set, which subsequently can be derived from a measured value provided by the physical token, is associated with each quantization interval. Further, information which subsequently enables determination of these quantization intervals is stored. Hence, an enrolling phase has been completed. When the preparing phase has been completed, a deriving phase may commence. When a data set is to be derived, for example to be used as a cryptographic key, a value of any one of the parameters provided by the PUF is measured. This measured value is quantized into a determined quantization interval, and a data set may be derived from the quantization interval into which the measured value is quantized.