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

With the application of blockchain in Internet of Things (IoT), various IoT scenario-oriented blockchains have been proposed, meaning that multichain future within IoT ecosystem is growing. Cross-chain interoperability thus is essential. Sidechains is one of the crucial technologies for cross-chain interoperability, which allows blockchains to interoperate with each other. However, sidechains encounters practicability challenges impeding adoption, such as poor generality and inefficiency. In this article, we propose practical and secure sidechain construction (PSSC)in the form of parent-child chains, a practical and secure sidechains construction for heterogeneous blockchains orienting IoT scenarios. To achieve practicability, we first utilize succinct noninteractive argument of knowledge (SNARK), which is succinct noninteractive proof (arguments) of knowledge, to reproduce the state transition of blockchains, so that PSSC can get rid of the constraints on consensus mechanisms of blockchains; we then design an impawn-punish mechanism based on smart contract, which transfers the work verifying SNARK proof from mainchain to sidechain, preventing fork threat to mainchain. Due to employing SNARK based on recursive proof composition to generate cross-chain proof, our PSSC is more efficient with succinct cross-chain proof, reducing the overhead of storage of nodes. Besides, we formally prove our PSSC satisfies the three fundamental security properties of sidechains: 1) persistence; 2) liveness; and 3) firewall. Finally, we develop a proof-of-concept implementation of PSSC, and the experimental results show that the proof size of PSSC is about 28.8 kB, which is roughly $2094\times $ , $9.36\times $ , $6.56\times $ , $4.23\times $ , and $3.27\times $ smaller than BTCRelay proof, PoW sidechains proof, PoS sidechains, zkRelay proof, and fast sidechains, respectively.