Stealth-MITM DoS Attacks on Secure Channels

We define stealth Man-in-the-Middle adversaries, and analyse their ability to launch denial and degradation of service (DoS) attacks on secure channels. We show realistic attacks, disrupting TCP communication over secure VPNs using IPsec. We present: First amplifying DoS attack on IPsec, when deployed without anti-replay window. First amplifying attack on IPsec, when deployed with a `small' anti-replay window, and analysis of `sufficient' window size. First amplifying attack on IPsec, when deployed with `sufficient' window size. This attack (as the previous) is realistic: attacker needs only to duplicate and speed-up few packets. We also suggest a solution designed to prevent the presented attacks, and to provide secure channel immune to degradation and other DoS attacks. Our solution involves changes (only) to the two gateway machines running IPsec. In addition to their practical importance, our results also raise the challenge of formally defining secure channels immune to DoS and degradation attacks, and providing provably-secure implementations.Comment: 14 figures; 21 page

An Anti-Replay Window Protocol with Controlled Shift

The anti-replay window protocol is used to secure IP against an adversary that can insert (possibly replayed) messages in the message stream from a source computer to a destination computer in the Internet. In this paper, we discuss this important protocol and point out a potential problem faced by the protocol, in which severe reorder of messages can cause the protocol to discard a lot of good messages. We then introduce a controlled shift mechanism that can reduce the number of discarded good messages by sacrificing a relatively small number of messages. We use simulation to show that the modified protocol is more effective than the original protocol when a severe reorder of messages occurs. In particular, we show that the modified protocol reduces the number of discarded good messages by up to 70%. I