Method for validating an identity of a designated functional device, the method comprising: - transmitting a control command signal for at least one component of the designated functional device to the designated functional device by an off-functional-device server unit, wherein transmission of the control command signal is triggered by a validation request signal received by the off-functional-device server unit from an off-functional-device communication device, wherein the off-functional-device server unit creates the control command signal for the at least one component of the designated functional device, wherein several control command signals are provided of which a current control command signal is chosen and transmitted to the designated functional device, wherein the current control command signal is chosen in specific time intervals and/or at a specific point in time; - operating the at least one component of the designated functional device according to the transmitted control command signal by a control unit of the designated functional device; - transmitting a request signal to an off-functional-device device requesting submission of specific measurement data of a functional device that is presumed to be the designated functional device by the off-functional-device server unit; - receiving the requested specific measurement data for the presumed functional device by the off-functional-device server unit; - evaluating the received specific measurement data by the off-functional-device server unit by applying a specific evaluation rule to determine if the at least one component of the presumed functional device was operated according to the transmitted control command signal; - if the at least one component of the presumed functional device was operated according to the transmitted control command signal, validating that the presumed functional device is the designated functional device. - transmitting a control command signal for at least one component of the designated functional device to the designated functional device by an off-functional-device server unit, wherein transmission of the control command signal is triggered by a validation request signal received by the off-functional-device server unit from an off-functional-device communication device, wherein the off-functional-device server unit creates the control command signal for the at least one component of the designated functional device, wherein several control command signals are provided of which a current control command signal is chosen and transmitted to the designated functional device, wherein the current control command signal is chosen in specific time intervals and/or at a specific point in time; - operating the at least one component of the designated functional device according to the transmitted control command signal by a control unit of the designated functional device; - transmitting a request signal to an off-functional-device device requesting submission of specific measurement data of a functional device that is presumed to be the designated functional device by the off-functional-device server unit; - receiving the requested specific measurement data for the presumed functional device by the off-functional-device server unit; - evaluating the received specific measurement data by the off-functional-device server unit by applying a specific evaluation rule to determine if the at least one component of the presumed functional device was operated according to the transmitted control command signal; - if the at least one component of the presumed functional device was operated according to the transmitted control command signal, validating that the presumed functional device is the designated functional device.