PSSC: Practical and Secure Sidechain Construction for Heterogeneous Blockchains Orienting IoT

With the application of blockchain in Internet ofThings (IoT), various IoT scenario-oriented blockchains havebeen proposed, meaning that multichain future within IoT ecosys-tem is growing. Cross-chain interoperability thus is essential.Sidechains is one of the crucial technologies for cross-chain inter-operability, which allows blockchains to interoperate with eachother. However, sidechains encounters practicability challengesimpeding adoption, such as poor generality and inefficiency.In this article, we propose practical and secure sidechain con-struction (PSSC) in the form of parent-child chains, a practicaland secure sidechains construction for heterogeneous blockchainsorienting IoT scenarios. To achieve practicability, we first uti-lize succinct noninteractive argument of knowledge (SNARK),which is succinct noninteractive proof (arguments) of knowl-edge, to reproduce the state transition of blockchains, so thatPSSC can get rid of the constraints on consensus mechanisms ofblockchains; we then design an impawn-punish mechanism basedon smart contract, which transfers the work verifying SNARKproof from mainchain to sidechain, preventing fork threat tomainchain. Due to employing SNARK based on recursive proof composition to generate cross-chain proof, our PSSC is moreefficient with succinct cross-chain proof, reducing the over head of storage of nodes. Besides, we formally prove our PSSC sat-isfies the three fundamental security properties of sidechains:1) persistence; 2) liveness; and 3) firewall. Finally, we develop aproof-of-concept implementation of PSSC, and the experimental results show that the proof size of PSSC is about 28.8 kB, whichis roughly 2094x, 9.36x, 6.56x, 4.23x, and 3.27xsmaller than BTC Relay proof, PoW sidechains proof, PoS sidechains, zkRelayproof, and fast sidechains, respectively.