ACM Transactions on Computer Systems (TOCS)
Low-cost client puzzles based on modular exponentiation
ESORICS'10 Proceedings of the 15th European conference on Research in computer security
Secure client puzzles based on random beacons
IFIP'12 Proceedings of the 11th international IFIP TC 6 conference on Networking - Volume Part II
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Client puzzles have been advocated as a promising countermeasure to denial-of-service (DoS) attacks in recent years. However, how to operationalize this idea in network protocol stacks still has not been sufficiently studied. In this paper, we describe our research on a multi-layer puzzle-based DoS defense architecture, which embeds puzzle techniques into both end-to-end and IP-layer services. Specifically, our research results in two new puzzle techniques: puzzle auctions for end-to-end protection and congestion puzzles for IP-layer protection. We present the designs of these approaches and evaluations of their efficacy. We demonstrate that our techniques effectively mitigate DoS threats to IP, TCP and application protocols; maintain full interoperability with legacy systems; and support incremental deployment. We also provide a game theoretic analysis that sheds light on the potential to use client puzzles for incentive engineering: the costs of solving puzzles on an attackers’ behalf could motivate computer owners to more aggressively cleanse their computers of malware, in turn hindering the attacker from capturing a large number of computers with which it can launch DoS attacks.