Censorship-resistant and privacy-preserving distributed web search

The vast majority of Internet users are relying on centralized search engine providers to conduct their web searches. However, search results can be censored and search queries can be recorded by these providers without the user's knowledge. Distributed web search engines based on peer-to-peer networks have been proposed to mitigate these threats. In this paper we analyze the three most popular real-world distributed web search engines: Faroo, Seeks and Yacy, with respect to their censorship resistance and privacy protection. We show that none of them provides an adequate level of protection against an adversary with modest resources. Recognizing these flaws, we identify security properties a censorship-resistant and privacy-preserving distributed web search engine should provide. We propose two novel defense mechanisms called node density protocol and webpage verification protocol to achieve censorship resistance and show their effectiveness and feasibility with simulations. Finally, we elaborate on how state-of-the-art defense mechanisms achieve privacy protection in distributed web search engines.