Method for communication of loT nodes or loT devices in a local network, which is at least temporarily connected to the Internet solely via a computer, wherein the local network is an Ethernet network or a single pair Ethernet network, wherein the loT nodes or the loT devices each have a first interface for communication in the local network with other loT nodes or with the computer, wherein each loT node or each loT device has a first public cryptographic key and a first private cryptographic key, the first private key being stored in advance or generated by the loT node or the loT device itself, having the step: authentication of IoT nodes or loT devices in a local network, characterized by - sending a request for a root certificate to a root-certificate server on the Internet by means of the computer, said root-certificate server having at least one root certificate from a manufacturer of the loT nodes or the loT devices, - receiving and storing the root certificate by means of the computer, and - checking by means of the computer whether the loT nodes or loT devices are original and unmodified devices by using the received root certificate, wherein the root certificate is suitable for linking the first public key of the loT nodes or loT devices to unique address information of the loT node or the loT device that is valid exclusively in the local network, wherein the computer uses the stored root certificate to check whether the public key of the loT node or the loT device is signed by the manufacturer of the loT node or the loT device, wherein the first private key of the loT node or the loT device is checked based on a cryptographic method, wherein the loT nodes or the loT devices are designed to be display-free and operating-element-free. authentication of IoT nodes or loT devices in a local network, characterized by - sending a request for a root certificate to a root-certificate server on the Internet by means of the computer, said root-certificate server having at least one root certificate from a manufacturer of the loT nodes or the loT devices, - receiving and storing the root certificate by means of the computer, and - checking by means of the computer whether the loT nodes or loT devices are original and unmodified devices by using the received root certificate, wherein the root certificate is suitable for linking the first public key of the loT nodes or loT devices to unique address information of the loT node or the loT device that is valid exclusively in the local network, - sending a request for a root certificate to a root-certificate server on the Internet by means of the computer, said root-certificate server having at least one root certificate from a manufacturer of the loT nodes or the loT devices, - receiving and storing the root certificate by means of the computer, and - checking by means of the computer whether the loT nodes or loT devices are original and unmodified devices by using the received root certificate, wherein the root certificate is suitable for linking the first public key of the loT nodes or loT devices to unique address information of the loT node or the loT device that is valid exclusively in the local network, wherein the computer uses the stored root certificate to check whether the public key of the loT node or the loT device is signed by the manufacturer of the loT node or the loT device, wherein the first private key of the loT node or the loT device is checked based on a cryptographic method, wherein the loT nodes or the loT devices are designed to be display-free and operating-element-free.