Re: MD5 authentication needs help -SCRAM

At 2015-03-14 09:44:02 +0200, hlinnaka(at)iki(dot)fi wrote:
>
> Perhaps it would be time to restart the discussion on standardizing
> SRP as a SASL mechanism in IETF.

I haven't seen much evidence that there's any interest in doing this; in
fact, I can't remember the author of the draft you pointed to being very
active in the discussions either.

> Assume that the connection is not encrypted, and Eve captures the
> SCRAM handshake between Alice and Bob. Using the captured handshake,
> she can try to guess the password, offline. With a PAKE protocol, she
> cannot do that.

OK. I agree that this is a nice property. SCRAM made the design decision
to hinder such attacks by using PBKDF2 rather than a zero-knowledge key
exchange mechanism as SRP does. This was partly due to the trend that I
mentioned of wanting to require TLS everywhere.

I'm obviously biased in this matter, but I think it's acceptable for the
potential attack to be frustrated by the use of PBKDF2 and defeated by
the use of TLS (which is already possible with Postgres); and that in
the balance, SCRAM is easier to implement securely than SRP.

Of course, if you want to use "x" as your password everywhere, then SRP
is preferable. ;-)

-- Abhijit

P.S. I don't know why the SRP code was removed from LibreSSL; nor am I
sure how seriously to take that. It's possible that it's only because
it's (still) rather obscure.