Ensuring scalability in cryptocurrency systems is significant in guaranteeing real-world utility along with the remarkable increment of cryptographic currency. As an alternative in solving scalability issue, payment channel allows users to deliver extensive offline transactions without uploading massive transaction details to the blockchain, such that increasing efficiency can be achieved. However, the implementation of payment channel still encounters privacy concerns when considering the publicly available transaction amounts and the potentials in mining associations between transaction parties. In this paper, we propose a novel payment channel scheme, entitledCommitment-basedAnonymousPayment ChannEl (CAPE), to facilitate unlimited off-chain bidirectional payments while guaranteeing participants’ privacy. The proposed scheme adopts zero-knowledge proof (zk-SNARKs) and verifiable timed (VTD) commitments to ensure the anonymity of the relationship between on-chain and off-chain transactions, privacy of transaction amounts, and security of balances. We comprehensively formalize security definitions and present rigorous proofs for each security attribute. Experiment results further demonstrate the practical viability of CAPE.

As a flourishing technical adoption boosted by 5G technology in recent years, Internet of Things (IoT) has become a common implementation in contemporary network-based solutions, such that tons of IoT devices, seen as nodes in the network, are employed. In order to meet the demands of the network edge, IoT devices mostly have limited computation and storage capabilities; however, this setting also introduces trust and security concerns. One of the noticeable threats is that malicious nodes forge or impersonate other legal nodes’ identities, which results in trustworthiness issues. In this article, we focus on the trust issue of IoT device identities and propose a cross-chain-based solution that applies a reply chain for identifying the legality of device nodes. Our proposed relay chain-based IoT model supports secure and reliable data transmission through the relay chain with the authorization and trust of all IoT blockchains. The relay chain realizes the multiparty verification of IoT devices; thus, addressing the trust problem of device identities. The consensus of the relay chain is executed by the arbitration committee nodes rather than all nodes. Considering the efficiency and adaptability, we also have proposed a novel optimal cross-chain decision-making algorithm to optimize the consensus for the identity-oriented relay chain. The proposed algorithm can minimize the cross-chain overhead while ensuring the fairness of the consensus. Our experiment evaluations have demonstrated that the proposed approach could increase the cross-chain efficiency under triple constraints.