Access to high-quality data resources is fundamental for generating insights, making decisions, and fostering innovation across various sectors. Data trading makes this possible, by which businesses, researchers, and developers can acquire the critical datasets necessary to propel forward-thinking developments. Traditionally, data trading is conducted through centralized platforms, which face challenges such as single points of failure and user mistrust. To address these issues, blockchain-based data trading protocols have been proposed, offering an alternative way for data trading with no trusted third-party involvement. However, ensuring trading atomicity (i.e. the data requester gets the data and the data owner gets the payment atomically) and data quality in the absence of a trusted third party is challenging. This paper introduces MSDT, a blockchain-based data trading protocol that guarantees trading atomicity and data quality. MSDT is a multi-subset data trading protocol, allowing users to verify data quality during the trading process. In MSDT, a state channel-based trading contract is designed, which reduces on-chain costs while ensuring transactions are executed atomically. Additionally, to deal with potential malicious behaviors of data owners, a staking mechanism and trading strategy are provided. Security and performance analyses demonstrate that MSDT ensures trading atomicity and data quality verification while maintains efficiency comparable to existing solutions.

Electronic voting is crucial for contemporary democratic processes. However, conventional systems often struggle with a single point of failure and insufficient support for intricate voting semantics, especially in ranked-choice elections requiring distinct ranking constraints. Although blockchain technology enhances fault tolerance and auditability, existing blockchainbased solutions primarily focus on simpler voting schemes, encountering difficulties in effectively verifying privacy-preserving ranked ballots. To address this gap, we propose AranVoting, an innovative blockchain-based ranked-choice voting scheme designed to ensure anonymity and fairness through homomorphic encryption. AranVoting employs a structured matrix ballot format alongside zero-knowledge proof to ensure the correctness of the ballot format. Furthermore, we introduce a smart contractdriven counting mechanism that facilitates the availability and transparency of ballot tallying through gradient incentive and committee election algorithms. Our security and performance evaluations demonstrate that AranVoting provides secure rankedchoice voting, effectively guaranteeing essential security properties such as anonymity, correctness, and verifiability while maintaining practicality and reasonable computational overhead throughout the voting process.

Electronic voting plays a crucial role in facilitating democratic and convenient decision-making in people’s lives. However, implementing an electronic voting system poses challenges, such as meeting the stringent security requirements for anonymity, fairness, and verifiability. Another concern is the performance degradation when dealing with a large number of voters. In this paper, we propose$S^{3}$Voting, a blockchain sharding-based e-voting scheme that addresses these challenges. By combining robust security and scalability,$S^{3}$Voting provides reliable technical support for conducting large-scale elections. Utilizing advanced technologies such asHomomorphic Time-Lock Puzzle (HTLP)andone-time ring signature, the system safeguards voters’ privacy and ballot confidentiality. The approach involves dividing voters and miners into smaller shards, and implementing shard managing mechanisms to ensure security and enhance system efficiency. Through thorough security analysis, we demonstrate that$S^{3}$Voting not only meets the fundamental security requirements of e-voting but also offers verifiability and strong robustness-essential elements for successful large-scale elections. Moreover, experimental results indicate that$S^{3}$Voting significantly reduces the computational burden on individual miners and minimizes system processing time compared to existing blockchain-based e-voting solutions.

The integration of blockchain with crowdsourcing improves data security, reduces single-point failure risks, and enhances trust and traceability in the system. However, this integration also leads to scalability issues because of the decentralized consensus mechanism of blockchain. While multiple chain architecture can enhance system throughput and offer functionality extensions, they often require complex token locking and release mechanisms to prevent double-spending attacks. This leads to a significant portion of funds being locked, thereby reducing overall fund liquidity. In this paper, we propose FishboneChain, consisting of one main chain and multiple child chains. Specifically, we address the scalability issue by leveraging child chains to offload the crowdsourcing task result submission and verification transaction pressure from the main chain, while each child chain can deploy various crowdsourcing protocols to enhance the functionality. Furthermore, we design a fund management contract and periodic task settlement mechanism, which allows requesters to lock a single fund on the main chain to manage task status across multiple child chains, thereby reducing the locked fund percentage and improving fund liquidity. Our scheme satisfies the security requirements of a crowdsourcing platform, such as fund security, robustness, and double-spending resistance. Performance analysis shows our scheme can improve the system throughput to 100 times that of the main chain and maintain the locked fund percentage below 20%.

Sharding significantly enhances blockchain scalability by dividing the entire network into smaller shards that reach consensus and process transactions in parallel. Nevertheless, two new issues emerge with the adoption of sharding. One issue involves the shrinking size of consensus groups, which leads to vulnerability in consensus. Most existing works introduce periodic shuffle mechanisms to mitigate this problem. Nevertheless, these measures necessitate stronger security assumptions and can only offer a probabilistic assurance of consensus security. Another issue is the challenge in processing cross-shard transactions posed by the isolation of shards. Existing approaches utilize two-phase commit (2PC) or relay transaction mechanisms to handle cross-shard transactions. However, these approaches are vulnerable to double cross-shard attacks from malicious shards and are unable to achieve immediate atomicity. In this paper, to address the vulnerable consensus issue and achieve instant atomicity in cross-shard transactions, we design a hybrid consensus mechanism that embeds a lightweight global consensus into parallel intra-shard consensus processes. The global consensus allows all consensus nodes to jointly process cross-shard transactions, achieving cross-shard transaction instant atomicity. It also records shard snapshots to facilitate shard auditing to defend against malicious shards. Furthermore, we consider the performance of the proposed mechanism, and design a dynamic shard management mechanism. The dynamic shard management mechanism reduces transaction congestion and maintains an appropriate number of shards based on the system’s state. We conduct analyses of potential attacks and prove that our approach ensures safety and liveness even in the presence of malicious shards. We also evaluate the performance of our system and compare it with both non-sharded and classic blockchain-sharding systems. The evaluation results demonstrate the efficacy of our approach in dealing with transaction congestion while astutely controlling the number of shards.

E-voting plays a vital role in guaranteeing and promoting social fairness and democracy. However, traditional e-voting schemes rely on a centralized organization, leading to a crisis of trust in the vote-counting results. In response to this problem, researchers have introduced blockchain to realize decentralized e-voting, but the adoption of blockchain also brings new issues in terms of flexibility, anonymity, and usability. To this end, in this paper, we propose WeVoting, which provides weight-based flexibility with solid anonymity and enhances usability by designing a voter-independent on-chain counting mechanism. Specifically, we use distributed ElGamal homomorphic encryption and zero-knowledge proof to achieve voting anonymity with weight. Besides, WeVoting develops a counter-based counting mechanism to enhance usability compared with those self-tallying schemes. By critically designing an honesty-and-activity-based incentive algorithm, WeVoting can guarantee a correct counting result even in the presence of malicious counters. Our security and performance analyses elaborate that WeVoting achieves high anonymity in weighed voting under the premise of meeting the basic security requirements of e-voting. And meanwhile, its counting mechanism is sufficient for practical demands with reasonable overheads.

E-voting plays a vital role in modern social life. However, traditional e-voting systems usually rely on a trusted third party and therefore non-verifiable and prone to a single point of failure. In recent years, many researchers have tried to turn to blockchain to eliminate the vulnerabilities of e-voting systems. However, blockchain-based e-voting brings new problems in protecting voters’ privacy and ballots’ confidentiality, and causes a great performance degradation. In this paper, we propose AvecVoting, an anonymous and verifiable blockchain-based e-voting scheme, providing both strong security and high performance. Specifically, we utilize threshold encryption and one-time ring signature to protect voters’ privacy and ballots’ confidentiality. Furthermore, to improve the performance, we introduce the concept "counter" to count the ballots. Through the carefully designed RandomSortition and reputation-based PayOff algorithms based on smart contracts, AvecVoting can achieve correct counting even when some counters are untrustworthy. Our security and performance analyses show that AvecVoting provides strong security such as anonymity, non-repeatability, confidentiality, verifiability, etc., and meanwhile overcome the performance issues caused by blockchain and provides good efficiency in both voting and counting stages.