A method for authenticating a current user of a first communication system with respect to a second communication system by means of a behavior-based authentication carried out using the first communication system and the second communication system , the first communication system comprising a mobile, portable communication system carried by the user and a first interface , which is configured to communicate with the second communication system , the first communication system comprising a first sensor , which is configured to detect data , the data encompassing behavior-based data of an individual intrinsic behavior of the user , the first sensor, serving as a movement sensor for detecting movements of the first communication system , being configured to detect movement data, serving as data , of a gross motor-related movement of the current user of the first communication system , the second communication system comprising a second interface and a third interface , the second interface being configured to communicate with the first communication system via the first interface , the third interface being configured to communicate with at least one activatable device , the second communication system comprising a second sensor , which is configured to detect data of the user , the method comprising: - receiving a first interim result of the behavior-based authentication from the first communication system by the second communication system via the first interface and the second interface , the first interim result having been generated by the first communication system , using the behavior-based data detected by the first communication system ; - generating a classification result by the second communication system from the first interim result and a second interim result, which was generated by the second communication system , using the data detected by the second communication system ; - evaluating the classification result according to a predefined examination criterion by the second communication system ; and - activating the device by means of a control signal by the second communication system via the third interface as a function of whether the classification result meets the examination criterion, the user being authenticated if the classification result meets the examination criterion. - receiving a first interim result of the behavior-based authentication from the first communication system by the second communication system via the first interface and the second interface , the first interim result having been generated by the first communication system , using the behavior-based data detected by the first communication system ; - generating a classification result by the second communication system from the first interim result and a second interim result, which was generated by the second communication system , using the data detected by the second communication system ; - evaluating the classification result according to a predefined examination criterion by the second communication system ; and - activating the device by means of a control signal by the second communication system via the third interface as a function of whether the classification result meets the examination criterion, <EOS>