Consequences of symmetric key cryptography in proposed system When considering the proposed system architecture, with a combination of public key cryptography for the users and symmetric key cryptography for the IoT de- vices, the consequences and impact of the different disadvantages mentioned above are negligible. To be more concrete, we respectively identify the following solutions or countermeasures to the three identified issues of above. – As the user already established a private-public key pair with the TTP during Phase 1, the secure channel can be easily set-up to transmit the IoT related security material of Phase 2. – It is correct that the TTP is able to derive all the secure session keys established between IoT and MEC node and thus can retrieve afterwards the raw data sent from IoT to MEC node while eavesdropping on that channel. However, the TTP is not able to derive the resulting outcome of the analysis performed by the MEC node as this is only sent to legitimate users, which are relying on their private key to construct the session key with the MEC node. Therefore, the costs for the TTP to derive interesting data will be too high and not be made, given the enormous reputation cost in case of being trapped. – The TTP cannot simply add new devices to the analysis profile of the user and let the devices send fake data, without being noticed by the user in the analysis reports sent by the MEC. Since these reports can be sent in an authenticated way with a guarantee on integrity, the TTP is not able to forge the reports.
