D(HE)at: A Practical DoS Attack on the Finite Field Diffie–Hellman Key Exchange

https://ieeexplore.ieee.org/document/10374117

by c0r0n3r • 2 years ago

37 13 2 years ago

ieeexplore.ieee.org

The linked article really beats around the bush before describing the attack. This link is a bit better: https://dheatattack.gitlab.io/dheater/ It honestly doesn't seem that impactful to me.

glitchc2• 2 years ago

Discussing cryptographic solutions to denial of service attacks always seem a tad disingenuous. In the MITM model, the attacker is in full control of the communications channel, and can always replace, corrupt or deny packets to either recipient. No amount/quality/degree of cryptography can change this possibility.

Retr0id2• 2 years ago

This attack doesn't require MitM, though.

glitchc2• 2 years ago

Yes, because Alice herself is malicious.

anonymous-panda2• 2 years ago

You’re misunderstanding the DOS attack I think. This is a DOS on the server itself and can prevent all other clients from connecting or the server from doing any useful work as its time is spent computing keys instead of anything useful. It doesn’t require any MITM proxy to be installed. Basically imagine a client could connect to a random Google server and take it down.

dboreham• 2 years ago

Yes but this is nothing to do with cryptography per se. Most servers can be taken down by a client that finds some expensive operation it can get executed, then sends a bunch of same. The solution implies a generic per-client or per-request resource limit mechanism (which in my experience some systems have, but most do not). This is probably the only good thing about "serverless"/lambda type solutions.

tptacek2• 2 years ago

Will Google even do a straight FFDH TLS handshake? I tried with s_client and couldn't find a cipher string that would work (starting by taking the default and just chopping all the non-DH strings out).

tptacek2• 2 years ago

Seems pretty boring. It's an unbalanced computation issue: the server sends B=g^b to the client, expecting the client to generate and send A=g^a. Instead, the client sends a random A, "proving no work" so to speak. Repeat. I think that's the whole attack?

mike_d• 2 years ago

This reads like a "I got funding but my original research didn't pan out and I need to publish something."

thadt• 2 years ago

This specifically (CPU exhaustion attack) is called out as a rationale for why Wireguard implements cookie reply packets[1]. If a verified source is DOSing you with bad handshakes, maybe its time for their IP to be put in timeout in an upstream routing table.

[1] https://www.wireguard.com/protocol/#dos-mitigation

D(HE)at: A Practical DoS Attack on the Finite Field Diffie–Hellman Key Exchange

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