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speakeasyjs / speakeasy

**NOT MAINTAINED** Two-factor authentication for Node.js. One-time passcode generator (HOTP/TOTP) with support for Google Authenticator.
MIT License
2.7k stars 228 forks source link

Valid usage question (using this in reverse) #130

Open SilentCicero opened 4 years ago

SilentCicero commented 4 years ago

Hi there,

Is it possible to use this library in reverse, such that the shared key is known by the user / attacker but the delta is not?

Such that, an attacker can generate the secret but will not know the time delay which only the user has?

I would think that has some interesting cryptographic properties if actually possible.

Best, Nick