1. A method for designing a circuit suitable for generating random bits, wherein the circuit comprises a number m of mapping devices, the method comprising: supplying a number n of input bits to each of the mapping devices, wherein n is a value greater than 1; implementing, by the mapping devices, a bijective mapping of n input bits to n output bits using a respective function; selecting a j-th mapping device from a first of the mapping devices to the m-th mapping device and prescribing a j-th specific function from a set of bijective mappings as the j-th function, wherein a j-th concatenation of the j functions carries out a j-th fixed-point-free mapping when the j-th specific function is prescribed as the j-th function; applying, by the j-th concatenation, the j functions in an ascending order starting with the first function; selecting at least one i-th mapping device from the first mapping device to the m-th mapping device, where i is not equal to j, and prescribing an i-th specific function from a set of bijective mappings as the i-th function, wherein an i-th concatenation of the i functions carries out an i-th fixed-point-free mapping when the i-th specific function is prescribed as the i-th function; applying, by the i-th concatenation, the i functions in an ascending order starting with the first function; and manufacturing the designed circuit suitable for generating random bits.