Smart contracts play a vital role in blockchain applications, supporting an expanding array of services as the number of blockchains rises. As service requirements become increasingly complex, the need for access and collaboration among multiple smart contracts becomes more prevalent. However, achieving access between smart contracts on different blockchains presents a significant challenge in the Internet of Blockchain scenario comprising numerous heterogeneous blockchains. In this paper, we first explore the problem of smart contract access in cross-heterogeneous blockchain scenarios. Then, an Oracle gateway-based cross-chain smart contract access architecture and a subscription-based cross-chain smart contract active access mechanism are proposed. Finally, a prototype is implemented to show that our architecture and mechanism can support cross-chain smart contract access for heterogeneous blockchains and reduce the complexity and latency of cross-chain smart contract access.

Edge Computing as a paradigm, provides services of outsourcing computations to a large number of end users. Since edge nodes are trustless, the integration of sampling-based replication calculation and the blockchain is used to verify the correctness of computation results in a trustless environment. However, the blockchain with the nature of decentralization, is confronted with some problems of high resource consumption, such that the verification with computational overhead cannot be directly deployed on the blockchain. Thus, we propose an accountable verification scheme based on an off-chain block. The off-chain block meets some requirements of Edge Computing, i.e., reduced latency of services, and edge nodes with heterogeneous resources. The off-chain block tries to address two challenges for reliable outsourcing computations: (i) how to generate the block efficiently and securely, and (ii) how to achieve accountable verification. In detail, the block is based on a Directed Acyclic Graph, in which the transactions of computation results and verification reports are updated in full decentralization. The hash of the block is recorded on the blockchain. Moreover, the integration of off-chain verification and on-chain arbitration provides reliable verification. A trust evaluation model achieves accountability for edge nodes. Besides, we conducted the security analysis based on some performance properties. Finally, the Raspberry Pis are leveraged to simulate lightweight edge nodes to prove the scalability of our outsourcing computations. A consortium blockchain with groups is also implemented to reveal the efficiency of blockchain updates of the proposed scheme.

Crowdsourcing as a computing paradigm, has been widely used in industries and services. Accountability in crowdsourcing services enables participants to work honestly and improves the quality of services. The realization of accountability requires trusted evidence, multiparty verification, and fair reward or punishment. Blockchain technology, which is inherently tamper-resistant, traceable, and decentralized, puts forward a direction for realizing the requirements. However, in the process of data management and decentralized verification, it is hard to achieve a better trade-off between efficiency and security. This paper proposes a blockchain-based verification scheme integrated by trust management, ‘validatorRep’, that is suitable to enhance accountability in the crowdsourcing system. In detail, a decoupled blockchain model is proposed for the differentiated storage of business transactions and log transactions during data interaction. Additionally, a fine-grained trust model is proposed, including both the rep-utation of participants and the trust relationship between participants. Based on fine-grained trust, the decentralized verification scheme is designed to guarantee secure data access, trusted verification, and fair reward or punishment. Finally, the proposed framework is deployed on the Ethereum platform to observe its effectiveness and overall performance. Simulation results also reveal that the proposed fine-grained trust model can provide efficient accountability for crowdsourcing.

EOSIO smart contracts are programs that can be collectively executed by a network of mutually untrusted nodes. As EOSIO smart contracts manage valuable assets, they become high-value targets and are subjected to more and more attacks. Tools for protecting EOSIO smart contracts are imperative. This paper proposes EOSIOAnalyzer, an effective static secu-rity analysis framework for EOSIO smart contracts to counter the three most common attacks. The framework consists of three components, the control flow graph builder, the static analyzer and the vulnerability detector. This paper implements an approach to transforming low-level Wasm bytecode into a high-level intermediate representation (Register Transfer Language). Besides, this paper also implements vulnerability detection speci-fications for three popular EOSIO smart contracts vulnerabilities, including Fake EOS Transfer, Forged Transfer Notification and Block Information Dependency. As a proof of concept, this paper conducts experiments to evaluate the effectiveness and efficiency of the EOSIOAnalyzer. The experiment results show that the detection accuracy of the three vulnerabilities is 100 %, 98.8 % and 100%, respectively.