A method for authenticating a current user of a mobile, portable communication system to a storage system by means of a behaviour-based authentication, wherein the communication system has at least one sensor for capturing user-related data, wherein the user-related data comprise information regarding the behaviour of the user, wherein the storage system comprises a memory, wherein the method performed by the communication system comprises the steps of: - generating at least one classification result with use of the user-related data for the behaviour-based authentication, - evaluating the at least one classification result in order to authenticate the user, wherein the evaluation comprises checking whether the classification result fulfils a predefined inspection criterion, wherein a successful authentication comprises a fulfilment of the inspection criterion, - generating an authentication signal on the basis of the result of the evaluation of the classification result and sending the authentication signal to the storage system, - granting access to the memory of the storage system if the authentication signal indicates a successful authentication of the user, wherein the user-related data comprise movement data regarding a movement of the communication system, wherein the movement of the communication system is caused by a gross-motor and/or fine-motor movement of the current user of the communication system whilst the user carries the communication device with him, wherein the sensor is configured to capture the movement of the communication system, wherein the behaviour-based authentication is performed by the communication system, which also has a classification module, a processor, and an internal memory, wherein the classification module is configured to classify the behaviour of the current user on the basis of the user-related data, wherein the classification module is also trained to identify a generic movement pattern with the aid of training datasets of a user cohort, wherein the classification module is executed by the processor of the communication system, wherein the behaviour-based authentication has the following steps: - repeatedly executing the generation of a confidence value, wherein the generation of the confidence value comprises the following steps: • capturing the user-related data by the at least one internal sensor of the communication system, • inputting the data into the classification module, • generating at least one first confidence value by the classification module, • storing the at least one first confidence value in the memory of the communication system, - in response to an authentication request, accessing the memory of the communication system in order to read out at least one of the generated and stored first confidence values from the memory, - generating the at least one classification result with use of the at least one first confidence value. - generating at least one classification result with use of the user-related data for the behaviour-based authentication, - evaluating the at least one classification result in order to authenticate the user, wherein the evaluation comprises checking whether the classification result fulfils a predefined inspection criterion, wherein a successful authentication comprises a fulfilment of the inspection criterion, - generating an authentication signal on the basis of the result of the evaluation of the classification result and sending the authentication signal to the storage system, - granting access to the memory of the storage system if the authentication signal indicates a successful authentication of the user, - repeatedly executing the generation of a confidence value, wherein the generation of the confidence value comprises the following steps: • capturing the user-related data by the at least one internal sensor of the communication system, • inputting the data into the classification module, • generating at least one first confidence value by the classification module, • storing the at least one first confidence value in the memory of the communication system, • capturing the user-related data by the at least one internal sensor of the communication system, • inputting the data into the classification module, • generating at least one first confidence value by the classification module, • storing the at least one first confidence value in the memory of the communication system, - in response to an authentication request, accessing the memory of the communication system in order to read out at least one of the generated and stored first confidence values from the memory, - generating the at least one classification result with use of the at least one first confidence value. - generating the at least one classification result with use of the at least one first confidence value.