In-network source authentication and path validation are fundamental primitives to construct higher-level security mechanisms such as DDoS mitigation, path compliance, packet attribution, or protection against flow redirection. Unfortunately, currently proposed solutions either fall short of addressing important security concerns or require a substantial amount of router overhead. In this paper, we propose lightweight, scalable, and secure protocols for shared key setup, source authentication, and path validation. Our prototype implementation demonstrates the efficiency and scalability of the protocols, especially for software-based implementations.

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We present the Crossfire attack -a powerful attack that degrades and often cuts off network connections to a variety of selected server targets (e.g., servers of an enterprise, a city, a state, or a small country) by flooding only a few network links. In Crossfire, a small set of bots directs lowintensity flows to a large number of publicly accessible servers. The concentration of these flows on the small set of carefully chosen links floods these links and effectively disconnects selected target servers from the Internet. The sources of the Crossfire attack are undetectable by any targeted servers, since they no longer receive any messages, and by network routers, since they receive only low-intensity, individual flows that are indistinguishable from legitimate flows. The attack persistence can be extended virtually indefinitely by changing the set of bots, publicly accessible servers, and target links while maintaining the same disconnection targets. We demonstrate the attack feasibility using Internet experiments, show its effects on a variety of chosen targets (e.g., servers of universities, US states, East and West Coasts of the US), and explore several countermeasures.

In-network source authentication and path validation are fundamental primitives to construct higher-level security mechanisms such as DDoS mitigation, path compliance, packet attribution, or protection against flow redirection. Unfortunately, currently proposed solutions either fall short of addressing important security concerns or require a substantial amount of router overhead. In this paper, we propose lightweight, scalable, and secure protocols for shared key setup, source authentication, and path validation. Our prototype implementation demonstrates the efficiency and scalability of the protocols, especially for software-based implementations.

No abstract