An anonymous and accountable authentication scheme for Wi-Fi hotspot access with the Bitcoin blockchain

Anonymous authentication can protect users' privacy and security when they access public Wi-Fi hotspots. However, most of the existing privacy-enhanced authentication schemes either do not consider users' accountability or they are inherently dependent on trusted third parties, and therefore are undeployable in practical settings. In this paper, we design and implement an access authentication scheme to simultaneously and efficiently provide anonymity and accountability without relying on any trusted third party. Our scheme is inspired by the recent progress of Bitcoin techniques such as Colored Coins and CoinShuffle protocol. We utilize the unmodified Bitcoin blockchain as the powerful platform to manage and determine ownership of access credentials in a peer-to-peer fashion and introduce a completely decentralized Bitcoin mixing protocol that allows users to anonymously exchange their access credentials offline. The verification path of access credentials is designed to support blacklisting and punishing misbehaving anonymous users. Our proposed scheme is compatible with the current Bitcoin system, and its effectiveness and feasibility in Wi-Fi hotspot access scenario are also demonstrated by security analysis and performance evaluation.