Abstract: An apparatus for determining one or several response bits includes a hardware element comprising a plurality of parameters, and a determination module for determining one or several response bits. The determination module is configured to perform the determination of each response bit of the one or several response bits depending on one or several challenge bits. In addition, the determination module is configured to determine each of the one or several response bits by means of one or several selection processes, wherein the determination module is configured to, in each selection process of the one or several selection processes, perform a selection of a parameter from two or several parameters of the plurality of parameters of the hardware element. Here, the determination module is configured to perform the selection of the parameter from the two or several parameters depending on a challenge bit of the one or several challenge bits.