[gtank]

It’s enough because of the underlying PAKE technique. The passwords do not directly become the key, and an unsuccessful bruteforce attempt breaks the session.

PAKE isn’t really new, but it’s certainly underused for how much it changes the password game: https://blog.cryptographyengineering.com/2018/10/19/lets-tal...

[throwaway415415]

The server can still bruteforce it though right?

[lotharrr]

(author of magic-wormhole here)

Nope, the server gets no more power than a random network attacker. The codes are single-use, enforced by PAKE, so an attacker (or the server) gets at most one chance to guess the code for any single execution of the program.