Secure Data Replication over Untrusted Hosts

Data replication is a widely used technique for achieving fault tolerance and improved performance. With the advent of content delivery networks, it is becoming more and more frequent that data content is placed on hosts that are not directly controlled by the content owner, and because of this, security mechanisms to protect data integrity are necessary. In this paper we present a system architecture that allows arbitrary queries to be supported on data content replicated on untrusted servers. To prevent these servers from returning erroneous answers to client queries, we make use of a small number of trusted hosts that randomly check these answers and take corrective action whenever necessary. Additionally, our system employs an audit mechanism that guarantees that any untrusted server acting maliciously will eventually be detected and excluded from the system.