A client device for the secured activation of functions of a client, a server device for providing a password for the client device, and corresponding methods. The client device has a storage unit for storing a plurality of service keys, each service key defining at least one function of the client and being allocated to a password, a receiving unit for receiving a password from a server, and a processing unit for comparing the plurality of service keys with the received password, for selecting the service key to which the received password is allocated, and for activating at least one function of the client which is contained in the selected service key.