Abstract: During the last few years, there has been considerable progress in the design of Byzantine tolerant replication systems. The current state of the art protocols perform very well on small-scale systems that are usually confined to local area networks. However, current solutions employ flat architectures that have limited scalability due to the communication cost and limited availability on WANS due to strong connectivity requirements.

We present the first hierarchical Byzantine tolerant replication architecture suitable to systems that span multiple wide area sites. The architecture confines the effects of any malicious replica to its local site, reduces message complexity of wide area communication, and allows read-only queries to be performed locally within a site for the price of additional hardware. A prototype implementation is evaluated over several network topologies and is compared with a flat Byzantine tolerant approach.

Short Bio: Cristina Nita-Rotaru is an Assistant Professor in the Department of Computer Sciences and a member of CERIAS (Center for Education and Research in Information Assurance and Security) at Purdue University. She joined Purdue in 2003, and established the Dependable and Secure Distributed Systems Laboratory (DS^2, http://projects.cerias.purdue.edu/ds2/). She is a recipient of NSF CAREER Award.

Her work is funded by the Center for Education and Research in Information Security and Assurance (CERIAS), by the Defense Advanced Research Projects Agency (DARPA), and by the National Science Foundation (NSF).