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Keywords: Decentralized privacy system, Smart contracts, Encryption, Ownership, Access control.

Yunmin He1,2 , Yu-Chi Chen1* , Zhong-Yi Guo1 , Raylin Tso3 , and Shaozhen Ye2

1 Department of Computer Science and Engineering, Yuan Ze University, Taiwan
2 College of Mathematics and Computer Science, Fuzhou University, China
3 Department of Computer Science, National Chengchi University, Taiwan * This email address is being protected from spambots. You need JavaScript enabled to view it.


Abstract

Recently, Zyskind et al. proposed a decentralized personal data management system which keeps privacy through blockchain and off-blockchain storage, so-called the decentralized privacy (DP) system. This system helps users ensure data ownership and fine-grained access control for third-party service providers. However, in this DP system, the permission power is delegated to blockchain and the users' data are stored in the off-blockchain distributed hashtable. Therefore, this induces extra communication overhead to connect these two distinct functionalities. In this paper, we present a conceptually simple solution directly from smart contracts with cryptographic primitives. This system is called the smart contract-based decentralized privacy (SCDP) system to overcome the above-mentioned efficiency issues. We propose the basic SCDP system as a warm-up to introduce the design principle based on symmetric encryption. Moreover, the strong SCDP system is provided by using ciphertextpolicy attribute-based encryption to support more flexible scenarios of access control and also eliminate some limitations of the basic system. Finally, we discuss some analyses in the aspects of security, access control, and data segmentation.


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