Subject: Re: I-D ACTION:draft-ietf-pppext-mppe-keys-01.txt

From: Vernon Schryver <[email-masked]>
Date: Mon, 11 Oct 1999 09:38:49 -0600 (MDT)

> From: David Wagner <[email-masked]>

> ...
> If the special prefix makes cracking 40-bit keys 100x easier, that
> will make a huge difference to anyone involved in vacuum-cleaner-style
> interception of PPTP traffic, and might just tip the scales in the
> favor of making such large-scale attacks practical.  Surely this
> can't be a desired feature of the protocol!

If we had standing to discuss MPPE, I bet we could come up with far worse
things to say about it than interesting but not compelling oddities of
its RC4 keying.  Even if we restricted ourselves to talking about its
security, MPPE is not what I would call wonderful.

> If you mean that security issues aren't appropriate for this forum,
> then I agree that this is off-topic.  I don't mean to be a pest,
> but I do believe that security was a stated goal of the drafts under
> consideration.

Nothing to do with MPPE is a stated or unstated goal for this working
group.  The MPPE document is merely one of the least offensive examples
of the use of the IETF printing press for unrelated work and the theft of
the IETF's imprimatur.  (More offensive or at least illuminating examples
of that problem are draft-terrell-math-ipaddr-ipv4-02.txt and
draft-terrell-ip-spec-ipv7-ipv8-addr-cls-02.txt)

> (I have specifically avoided discussing any historical, sociological,
> political, or commercial issues, so I don't know why you brought it up.)
>
> Maybe I'm naive, but if there's a security flaw -- or a credible
> possibility of a security flaw -- in the protocol, shouldn't it be
> fixed with all due speed?

As you and I have discussed before, MPPE is a proprietary protocol that
that not even Microsoft could change, even if it wanted to, not to mention
whether it were willing to pay attention to concerns or suggestions from
the IETF.  (See the new version of MS-CHAP current evidence of Microsoft's
interest in playing with the IETF instead of continuing it's de facto if
perhaps unintentional embrace-and-extend strategy.)

Vernon Schryver    [email-masked]