Privacy-preserving Trust Management for Blockchain-based Resource Sharing in 6G-IoT

6G-enabled IoT demands effectively utilising scarce resources to provide massive scale in network capacity. While blockchain-based resource sharing schemes have been proposed to enable effective resource allocation, they alone cannot ascertain the trust in the participating nodes, as they do not monitor node activities during the resource sharing. Trust and Reputation Management (TRM) can potentially solve these trust issues. However, changeable keys employed in blockchains to improve privacy preservation may render the TRM unusable, as the same node is no longer identifiable by a single key to which the trust and reputation scores are bound. This paper proposes a privacy-preserving TRM for blockchain-based resource sharing in 6G-enabled IoT networks. Our solution employs interconnected public-private blockchains, namely Isolated Identity Chain and Main Resource-sharing Chain to protect nodes' identity. Our TRM framework allows the nodes to use changeable keys in each transaction, making it impossible to trace the sharing history. The experimental results on a proof-of-concept implementation indicate the feasibility of our framework as it only incurs minimal overheads.