loT-authentication server for authentication of a network device with a SIM-card, the loT-authentication server comprising: - a processor configured to: - store a dataset linking a unique identification of the SIM-card and a given set of specific credentials in a memory of the loT-authentication server, - receive an authentication request comprising a candidate unique identification of the network device and a candidate set of credentials; - retrieve a unique identification of the network device specified in a network layer of a public communication network transmitting the authentication request; and - generate an authentication-label for labelling the network device as authenticated only in case the unique identification of the network device specified in the network layer of the public communication network transmitting the authentication request matches the candidate unique identification of the network device specified in the authentication request, and the candidate set of credentials transmitted to the loT-authentication server from the network device using the SIM-card matches the specific credentials linked with the unique identification of the SIM-card in the dataset, wherein the processor is further configured to: - enable a communication between a target server and the network device only in case the network device is labelled as authenticated, and - communicate with the network device via a gateway of the public communication network, wherein the gateway is a network -server that is configured to register the SIM-card for communication via the public communication network. - a processor configured to: - store a dataset linking a unique identification of the SIM-card and a given set of specific credentials in a memory of the loT-authentication server, - receive an authentication request comprising a candidate unique identification of the network device and a candidate set of credentials; - retrieve a unique identification of the network device specified in a network layer of a public communication network transmitting the authentication request; and - generate an authentication-label for labelling the network device as authenticated only in case the unique identification of the network device specified in the network layer of the public communication network transmitting the authentication request matches the candidate unique identification of the network device specified in the authentication request, and the candidate set of credentials transmitted to the loT-authentication server from the network device using the SIM-card matches the specific credentials linked with the unique identification of the SIM-card in the dataset, - store a dataset linking a unique identification of the SIM-card and a given set of specific credentials in a memory of the loT-authentication server, - receive an authentication request comprising a candidate unique identification of the network device and a candidate set of credentials; - retrieve a unique identification of the network device specified in a network layer of a public communication network transmitting the authentication request; and - generate an authentication-label for labelling the network device as authenticated only in case the unique identification of the network device specified in the network layer of the public communication network transmitting the authentication request matches the candidate unique identification of the network device specified in the authentication request, and the candidate set of credentials transmitted to the loT-authentication server from the network device using the SIM-card matches the specific credentials linked with the unique identification of the SIM-card in the dataset, - enable a communication between a target server and the network device only in case the network device is labelled as authenticated, and - communicate with the network device via a gateway of the public communication network,