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Comment by tredre3 | Hacker News Reader

> A modern consumer GPU can crack "four random English words" in a day. [...] but arguing that that scheme is actually secure is just wrong.

Let me do just that!

This is a networked service. You send your password (or a hashed form) to it, and it validates it. You don't have the local hash to bruteforce it offline.

Even if we only consider the top 10k english words, it's 10000^4. It's going to take years to bruteforce this over a network because you'll go through so many rate-limits, cooldown periods, and outright bans that it's questionable whether it's even possible.

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Virtually any password other than "password123" is fine if you're rate limited to a few guesses per day by a networked service. Passwords should be secure against the inevitable data breach when the service you're using loses their hashed password database, which happens on a routine basis.

Seems like the only real issue here is that rustdesk uses SHA256 instead of argon2.

> This is a networked service. You send your password (or a hashed form) to it

Hopefully neither. But given everybody involved in VNC seems to be the same batch of clueless morons who built all those PHP web forums twenty years ago with MD5 as the password hash, who knows what they cobbled together. Maybe an expert can chime in about what actually happens here?

Yes, for a sensible scheme this can't work.

I’m not an expert in RustDesk, but I did take a quick look at the code, and it’s filled with massive red flags like [1], where it appears the general mechanism is SHA256(SHA256(password++salt)++challenge). I can’t even tell if the whole thing is vulnerable to trivial MITM ([2] makes it sound like it might be; while investigating, I ran into the concerning comment [3], “fall back to non-secure connection in case pk mismatch”). I can’t find any actual documentation of the protocol and it’s a custom thing built on NaCl boxes, yikes. [4] generates a keypair on the fly for a new connection to sign the box containing the symmetric key generated at the same time…

I would recommend never using this software.

[1]: https://github.com/rustdesk/rustdesk/blob/7aa98d43cf1962a7a2... [2]: https://github.com/rustdesk/rustdesk/discussions/8392 [3]: https://github.com/rustdesk/rustdesk/blob/7aa98d43cf1962a7a2... [4]: https://github.com/rustdesk/rustdesk/blob/7aa98d43cf1962a7a2...

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