A method for achieving a security function for a security control device for controlling a device or an installation, including: a) providing at least one first partial secret that is stored in a basic control device, b) providing at least one second partial secret that is stored in a security module, c) combining the at least one first and second partial secret to form an overall secret, required to achieve the security function, within the time period in which the basic control device interacts with the security module via the first and second coupling interfaces, and d) disguising the combined overall secret outside the time period.