[curves] Use cases for PAKE?
trevp at trevp.net
Wed Mar 19 11:30:54 PDT 2014
One thing we could discuss is Elliptic Curve PAKEs (Password Authenticated
There's some ideas worth exploring due to expiry of Lucent patents;
developments such as SPAKE2, J-PAKE, and AugPAKE; and "hashing to curve"
algorithms like SWU and Elligator [1,2]. For example, Mike Hamburg's ideas
in  seem promising.
But are there good use cases to focus discussion? Possibilities -
* PAKE for the web has been attempted in TLS (RFC 5054) with little
interest from browsers or sites. Partly this is a layering problem
(username in clear, too early in the connection, and the TLS terminator is
the wrong place for client auth). But there are deeper UI problems:
browsers would have to display an unspoofable dialog; users would have to
be trained to enter certain passwords only into this dialog; and sites
would lose control of login UI. Client auth for the web seems likely to
evolve in other directions (e.g. password managers, 2-factor, federation).
* SSH already has J-PAKE which (I think?) is rarely used, though I'm not
sure why. If part of the reason is performance, is there room for
* IEEE 802.11s I think has standardized on "Simultaneous Authentication of
Equals" (aka Dragonfly) as an EC PAKE. I don't know if it's seen real
deployment, nor do I understand the "mesh networking" scenario it's being
used for, which seems different from just authenticating a client to an AP.
Anyone know more?
* There are smaller, more specialized uses of PAKE for protocols like
online backups or device pairing. E.g. I think Chrome is (using?
investigating?) SPAKE2 for "chromoting", whatever that is.
Anyways, it's not clear that there are strong-enough use cases to motivate
a good discussion and keep it on track. Though I wish there were! PAKEs
are cool, it seems like they should be useful somewhere.
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