Increasing protection and autonomy in the IoT through a two-tier blockchain framework

In this paper, we propose an approach that uses a two-tier blockchain framework and a trust-based protection mechanism to increase the security and autonomy of smart objects in the IoT. The proposed approach groups the involved smart objects into suitable communities. The two blockchains perform different, but complementary, tasks. Indeed, the first-tier blockchain is local and records probing transactions performed to evaluate the trust of one smart object in another. Periodically, after a time window, the probing transactions are aggregated to determine the reputation of each smart object within its community and the trust of one community in each of the others. These values are stored in the second-tier blockchain. This paper describes the proposed approach, the underlying framework, the behavior, the security model and a test carried out to evaluate its performance.