Abstract: Data transmitted in a system having at least three instances is authenticated between two of these instances. Some of the instances implement an authentication mechanism so that a first instance can authenticate itself to a neighboring instance trusting the first instance. The data to be transmitted by the first instance as a source instance to a non-neighboring target instance is authenticated by the source instance and passed to an intermediate instance that trusts the source instance. The intermediate instance checks the authentication and provides the data with the identity label of the source instance, reauthenticates the data, and passes it to a neighboring instance trusting the intermediate instance. The neighboring instance checks the authentication, reauthenticates the data provided with the identity label of the source instance and passes it to a neighboring instance that trusts it, this process being repeated until the data to be transmitted reaches the target instance.

Abstract: A method involves a vehicle certification authority and a control device certification authority having a respective infrastructure for public keys based on an asymmetric pain of is established. The respective private key remains in the certification authority and the public key is distributed to the participants. The control device has initial cryptographic material by a control device-individual pair of keys being generated for the control device and the identity of the control device and its public key are transmitted to the control device certification authority, after which a control device-individual certificate is generated there for the transmitted data using the private key of the control device certification authority and transmitted back to the control device. The public key of the vehicle certification authority is stored in a tamper-proof manner in the control device. The vehicle identity belonging to the identity of the control device is determined and stored in a tamper-proof manner.

Abstract: A method involves a vehicle certification authority and a control device certification authority having a respective infrastructure for public keys based on an asymmetric pair of is established. The respective private key remains in the certification authority and the public key is distributed to the participants. The control device has initial cryptographic material by a control device-individual pair of keys being generated for the control device and the identity of the control device and its public key are transmitted to the control device certification authority, after which a control device-individual certificate is generated there for the transmitted data using the private key of the control device certification authority and transmitted back to the control device. The public key of the vehicle certification authority is stored in a tamper-proof manner in the control device. The vehicle identity belonging to the identity of the control device is determined and stored in a tamper-proof manner.

Abstract: A communication device for a vehicle has a communication unit set up to establish a communication link between the vehicle and an external vehicle server and to exchange data in a cryptographically secured manner between the vehicle and the external vehicle server. The communication unit is further set up to be operated in a first or second mode. The modes differ in the type of cryptographic securing of the data. The communication unit has a secure hardware memory in which a binary value corresponding to the respective mode is stored.