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In the post-epidemic era, the prevalence of remote collaborations in modern work environments highlight the importance of e-voting as a critical component in facilitating distributed decision-making. Most of the existing e-voting systems heavily rely on a centralized tally authority which requires a high degree of moral trust. However, this kind of architecture is insufficient for expected decentralization and verifiability in remote decision-making. A self-tallying e-voting system is more in line with our developed demands, nonetheless, it suffers adaptive and abortive issues inherently and as a result, fairness cannot be guaranteed. In this paper, we try to provide rational trust by building a blockchain-based self-tallying e-voting system with public traceability. We improve fairness and achieve a balance between privacy and accountability by taking advantage of a time-lock puzzle and traceable ring signature, in which the puzzle-solving time does not impose a real burden. We propose a concrete construction and prove that our protocol satisfies time-limited ballot secrecy, anonymity, exculpability, public traceability, self-tallying and fairness. We implement the prototype both on-chain and off-chain, and the results of time overhead of each phase demonstrate the practicability of our proposal. • Propose a self-tallying e-voting with public traceability based on blockchain. • Introduce a traceable ring signature to balance the anonymity and accountability. • Prove a detailed security proof for the protocol. • Evaluate the time cost of off-chain functions and on-chain functions. [ABSTRACT FROM AUTHOR]

• We propose a blockchain-based Verifiable privacy-preserving Data Classification protocol (VeriDC) for medical data. • We define the system model of the verifiable privacy-preserving data classification protocol in blockchain setting and formalize its security model. • We propose a concrete VeriDC protocol by using verifiable OPRF. We prove the security of VeriDC protocol in the random oracle model and compare VeriDC with the related scheme to evaluate the effectiveness of VeriDC. Massive IoT devices are used for data collection with the fast development of the Internet-of-things (IoT). For example, wearable devices are used to collect users' health data and conduct health monitoring. However, many private information are involved in medical data. Privacy-preserving data classification scheme (PPDC) provided an effective approach to balance the utility and the privacy of data. In the PPDC schemes, a fully trusted auditor is employed to validate the result of data classification. To reduce trust on the auditor, we provide a simplified version of the PPDC scheme. We propose blockchain-based verifiable privacy-preserving data classification protocol (VeriDC) for medical data. It makes the data center check the classification result without involving an auditor. We provide the system model of the verifiable privacy-preserving data classification protocol in blockchain setting and formalize its security model. By using verifiable oblivious pseudorandom function(verifiable OPRF), we can generate a verifiable proof and post it on blockchain to guarantee the transparency of data classification. We present a concrete construction and prove its security. Finally, we compare VeriDC with the related schemes to evaluate the effectiveness of VeriDC. [ABSTRACT FROM AUTHOR]

• Propose a blockchain-based accountable outsourcing data storage protocol. • Provide an accurate and verifiable damage assessment method. • Prove the security in detail of the protocol. • Evaluate the time cost of off-chain functions and the gas cost of on-chain functions. Outsourcing data integrity auditing enables users to efficiently check whether their cloud data are stored intactly without retrieving them. However, a problem arises that how to hold the storage server accountable when the auditing results show that the data has been lost or tampered with. In this paper, we propose a blockchain-based accountable data outsourcing storage protocol, which enables users to obtain fine-grained compensation based on the damage of data. We provide an accurate and verifiable damage assessment method to achieve quantitative compensation. Specifically, the damage is assessed by the server and verified by smart contract. Furthermore, our protocol ensures the fairness of participants by deposit mechanism and smart contract. If any participant behaves dishonestly, it cannot obtain any benefit or even be punished. To reduce user's overhead, we propose a new provable data possession scheme, PDP in short, supporting outsourcing the calculation of tags. Moreover, we provide a detailed security proof for the proposed protocol as well. Finally, we evaluate the time cost of off-chain functions and the gas cost of on-chain operations for our protocol, which demonstrates that it is practical and suitable in reality. [ABSTRACT FROM AUTHOR]