An Anonymous BlockchainBased Logging System for Cloud Computing Cloud computing has been in increasing concentration these years. Nevertheless, recently, it suffers the ambiguity in discerning responsibilities for unexpected incapable services. At this time, people refer to the logs. However, since logs may judge the fault, they are susceptible to malicious modification. Thus, their integrity is vital. Existing solutions leverage blockchain technology to tackle this problem, but few of them take the pseudoanonymous nature of blockchain into considerations. This risks usersxe2x80x99 privacy when they anchor their logs onto the blockchain. Some solutions try to be anonymous, but they are not general enough to be practical. In this paper, we propose a blockchainbased anonymous logging system for cloud environment. Our system introduces zeroknowledge proof to realize anonymous authentication, which can ensure undeniability in auditing while doing no harm to anonymity. Through experimental evaluation, we evaluate the feasibility and anonymity of the proposed system.

Security and Privacy on Blockchain Blockchain offers an innovative approach to storing information, executing transactions, performing functions, and establishing trust in an open environment. Many consider blockchain as a technology breakthrough for cryptography and cybersecurity, with use cases ranging from globally deployed cryptocurrency systems like Bitcoin, to smart contracts, smart grids over the Internet of Things, and so forth. Although blockchain has received growing interests in both academia and industry in the recent years, the security and privacy of blockchains continue to be at the center of the debate when deploying blockchain in different applications. This paper presents a comprehensive overview of the security and privacy of blockchain. To facilitate the discussion, we first introduce the notion of blockchains and its utility in the context of Bitcoin like online transactions. Then we describe the basic security properties that are supported as the essential requirements and building blocks for Bitcoin like cryptocurrency systems, followed by presenting the additional security and privacy properties that are desired in many blockchain applications. Finally, we review the security and privacy techniques for achieving these security properties in blockchainbased systems, including representative consensus algorithms, hash chained storage, mixing protocols, anonymous signatures, noninteractive zeroknowledge proof, and so forth. We conjecture that this survey can help readers to gain an indepth understanding of the security and privacy of blockchain with respect to concept, attributes, techniques and systems.