CRAB: 使用者可反駁的匿名廣播

Abstract

匿名廣播有很多應用，如吹哨者和電子投票。一些研究是基於混合網路，它們往往需要高成本的混合證明。一些研究是基於多方運算，混合成本較低，但使用者無法驗證其訊息的完整性。在這篇論文中，我們提出了CRAB，一個基於多方混合協定的匿名廣播系統，為使用者提供驗證機制。該系統是「使用者可反駁」的，意味著使用者可以證明伺服器的錯誤行為。我們證明了CRAB滿足安全性的需求。我們也顯示了CRAB可以應用於電子投票系統。最後，我們實作並評估了我們的系統。我們的系統可以比使用混合證明的系統快23～33倍，並且有良好的可擴展性。因此，我們的系統適用於大規模的電子投票。

There are many applications of anonymous broadcast, such as whistleblowing and electronic voting. Some works are based on mixnet, and they often require high cost on proof of shuffle. Some works are based on multiparty computation (MPC), where the shuffle cost is lower but the clients cannot verify the integrity of their messages. In this thesis, we propose CRAB, an anonymous broadcast system based on a multiparty shuffling protocol that provides a verification mechanism for the clients. The system is "client-rebuttable", which means that a client can prove the misbehavior of the servers. We prove that CRAB satisfies the security requirements. We also show that CRAB can be applied to electronic voting systems. Finally, we implement and evaluate our system. Our system can be 23~33 times faster than those using proof of shuffle, and our system has good scalability. Thus, our system is suitable for large-scale electronic voting.