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— The overall efficiency, reliability, and availability of a firewall is crucial in enforcing and administrating security, especially when the network is under attack. The continuous growth of the Internet, coupled with the increasing sophistication of the attacks, is placing stringent demands on firewall performance. These challenges require new designs,(More)
Various cryptographic puzzle schemes are proposed as a defense mechanism against denial of service attack. But, all these puzzle schemes face a dilemma when there is a large disparity between the computational power of attackers and legitimate clients: increasing the difficulty of puzzles might unnecessarily restrict legitimate clients too much, and lower(More)
In this paper, we present Productive Puzzles, a novel puzzle mechanism for defending against Distributed Denial of Service (DDoS) attacks. Productive puzzles aim to use tasks from real applications and services — as opposed to repetitive cryptographic computations that only serve the security purpose — as the work to be completed by the client, therefore(More)
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