Intrusion-tolerant server architecture for survivable services

Survivable systems are increasingly needed in a wide range of applications. As a step toward realizing survivable systems, this paper presents architecture of intrusion-tolerant servers. It is to deliver intended set-vices transparently to the clients even when a computing node fails due to failures, intrusions, and other threats. In order to deliver only secure results to the client, we need an algorithm to decide agreement on results from replicated servers. For this purpose, a secure and practical decentralized voting algorithm for the architecture is proposed in the paper. Through the experiments on a test-bed, especially, for web services, the approach turned out very effective in terms of extra cost and considered to be able to cope with both confidentiality and integrity attacks.