A Novel Oracle-Aided Industrial IoT Blockchain: Architecture, Challenges, and Potential Solutions

Smart contract over the blockchain accelerates the deployment of decentralized Industrial Internet of Things (IIoT) applications. However, the usability of smart contracts is constrained to the data on the blockchain, and has no direct access to the off-chain environment. Consequently, smart contract cannot directly serve as a carrier for the IIoT applications that rely on intensive data exchange and task computation. To cope with this issue, we first propose an oracle-aided IIoT blockchain (OIB) system to facilitate the deployment of smart contract based IIoT applications. Specifically, a distributed oracle network is employed to not only bridge the off-chain environment and smart contracts, but also extend the computing capability of smart contracts. Then, we study important properties of the OIB system, that is, liveness, safety, and fairness. In particular, we propose a new challenge of fairness to guarantee that each oracle can reap positive utility (i.e., individual rationality), and a new challenge of liveness to meet delay constraints of oracle services (i.e., delay-sensitivity). To address these two challenges, we develop an auction based incentive mechanism for the data-feeding oracles to achieve individual rationality as well as incentive compatibility, and a delay-sensitive matching based incentive mechanism for the computing oracles under specific delay constraints. Simulation results corroborate that the proposed auction based incentive mechanism guarantees not only truthfulness but also individual rationality, and show that the matching based incentive mechanism achieves smaller delay than the random selection scheme used in the Decentralized Oracle Service (DOS) network.