부산대학교 도서관

Blockchain is the most promising technology to tackle the security challenges of certificate revocation schemes, such as vulnerability to the single point of failure and lack of accountability systems. However, current blockchain-based certificate revocation systems suffer from privacy problems as the blockchain nodes can learn which website the client is going to connect with and infer the end-user's private information, such as identity, location, and health condition. In this paper, we propose a decentralized certificate revocation scheme that allows clients to securely and privately verify revocation information. We not only take advantage of blockchain to provide security guarantees but also further craft a novel multi-server offline/online private information retrieval (PIR) protocol named MOO-PIR to preserve query privacy for clients even if a subset of servers collude. Finally, we provide security analysis and performance evaluation, demonstrating that our scheme can protect client privacy without compromising efficiency.