I've been studying the OPAQUE protocol, and I like it (so far).

The RFC suggests using Argon2 as the Key-Stretching Function. Argon2 can take an optional "Secret value" (2, page 5).

I had the idea that that secret value could be provided by a Yubikey, so that the resulting OPAQUE protocol could use "something you have" (Yubikey) and "something you know" (password).

Is this possible? Is it even a good idea?

  • 2
    $\begingroup$ You could of course make the argument that a Yubi could be impersonated/synthesised unless it has PUF qualities. So you wouldn't have 2F authentication. $\endgroup$
    – Paul Uszak
    Jun 27, 2022 at 22:48
  • $\begingroup$ Fair enough. I guess I thought it would be "good enough." $\endgroup$ Jun 28, 2022 at 1:34


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