Re: [Cfrg] aPAKE Analysis / Why System-Level-View

[Natanael <[e-mail]>]

Den sön 22 sep. 2019 21:32Björn Haase <[e-mail]> skrev:

>
> > Being able to trigger a PAKE from a button press on your 2FA hardware
> > token would also be a significant UX improvement over many of the
> > other options with similar security level.
> >
> Do I correctly understand that you had in mind: The user first
> establishes a normal https:// connection and then presses the 2FA
> hardware switch in order to run a PAKE in addition to the previous
> certificate-based authentication?
>

Wouldn't have to be the default, but I'm considering a version of this;

If the server tells the client that it supports both hardware 2FA and PAKE,
and that they are supported together (and this flag could be cached on the
client so it can alert on downgrade), then yes.

It would perform HW 2FA auth on button press (may include certificates) and
then trigger PAKE. The user types the password and hits OK. Done.


> This is not what I assumed. What I had in mind is rather the following
> procedure. The server knows its requirements regarding security, etc. .
> The user and the browser don't know the required procedure in advance
> when connecting. If the server is needing 2FA, it would arrange the
> client to provide the aPAKE password entry mask and provide a "Please
> press authentication token switch for authentication".
>
> Did I actually mis-understand your post?
>

Your approach seems to be slightly different. So the browser first opens
the PAKE prompt and you then verify with the token? Presumably the browser
informs the user that the current webpage has PAKE support, they click to
open the prompt, and confirm with HW 2FA verification?

While functionally similar, the difference is in the UX security.

With your approach one could more easily get the user password through
phishing by showing them fake login prompts (and in a targeted attack, the
token could then be stolen).

A user that has been successfully taught that the password must only be
entered in the prompt after pressing the HW 2FA button will not type their
password into phishing prompts.

>