Method of detecting an unauthorized exchange of components in the case of a technical system, where the control unit (1) sends an encoded message (3) to a component (2) to be checked, in a data field of the message (3) a randomly generated or not easily reproducible value (5, 6) being entered, which is used for checking the installed component (2). The component (2) accesses an assignment field (8) and, as a result, assigns an identification (9) to each not easily reproducible or random value (5, 6) transmitted together with the message (3), and the component (2) transmits the identification corresponding to the value (5, 6) back to the control unit (1). The control unit (1) decides on the basis of the identification (9) whether the component (2) is that the component (2) which is authorized for use in the particular technical system.