The present invention relates to a method for generating and imprinting a retrievable cryptographic key during the fabrication of a topographic structure, in particular for microelectronic or micromechanical components. In the method a multiplicity of measuring circuits (11) is generated in the topographic structure, which measuring circuits each dependent on a value of at least one electrical or physical property in the topographic structure, which is subject to random fluctuations during the fabrication of the topographic structure containing the measuring circuits (11), generate a measuring value. The cryptographic key is formed or derived from the measuring values of the measuring circuits (11). The measuring circuits (11) are composed of three-dimensional electrical line structures (9, 10), each of which is provided with a random design and is generated in the topographic structure, and generate the measuring values dependent on the value of a parasitic electrical property of the line structures (9, 10).