BCSolid: A BlockchainBased Decentralized Data Storage and Authentication Scheme for Solid. Solid (Social Linked Data) aims to radically change the way web applications work today, giving users true data ownership and improved privacy. However, it is facing two challenges, one is that data in centralized repositories needs to be separated from social web applications that force users to share their information. In addition, a decentralized authentication that guarantees who can operate on userxe2x80x99s data with a secure privacy protection is another significant issue. In this paper, we address these challenges by proposing a blockchainbased decentralized data storage and authentication scheme for Solid, termed BCSolid, in which a userxe2x80x99s data can be independent of multiple web applications and can switch data storage service easily without relying on a trusted third party. Meanwhile, our scheme gurantees data ownership and userxe2x80x99s privacy by leveraging the blockchain miners to perform authentication with the help of certificateless cryptography. Additionally, we present a possible instantiation to illustrate how xe2x80x9ctransactionsxe2x80x9d in BCSolid are processed. To our knowledge this is the first work to promote the Solid project using blockchain. The evaluation results show that our scheme can gurantee a low latency network and is a promising solution to Solid.

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.