Subject: Re: Last Call: Telnet Authentication Option to Proposed Standard

From: Jeffrey Altman <[email-masked]>
Date: Tue, 23 Nov 99 17:35:39 EST

> Protocols that offer increased complexity but no gain in security or 
> efficiency over other standards-track efforts, but are in use today, are 
> IMHO excellent candidates for Informational publication.
> 
> Not for the standards track.

I think the point of this debate is whether or not there is added
strength to the encryption.  And so far the opinions have been
divergent.  If 3DES is a better PRNG than DES then it is stronger.

As we point out in the Drafts, the telnet encryption stream mechanism
is susceptible to attacks.  We know that.  We have addressed it in 
various ways.  Unfortunately, the Telnet AUTH option implementations
for Kerberos 4, Kerberos 5, and Secure Remote Password all rely on the
Telnet Encryption option for privacy.  I don't think it is appropriate
to send Telnet Auth to Proposed Standard with its reliance on an
option that is Informational.  Hence, the desire for all of these
drafts to go to Proposed Standard.

The TN3270 WG is working on a Telnet over TLS draft which has seen
several independent interoperable implementations for TN3270 and well
as more traditional telnet.  My hope is to integrate Telnet over TLS
with Telnet AUTH so that Telnet AUTH may be used to provide mutual
authentication via a TLS using an ADH cipher.  The one problem I have
run into is that the TLS Library vendors (other than OpenSSL) have
been very resistent to exporting the contents of the Finished messages
to the application so that they may be used in the Telnet Auth
negotiation to provide mutual authentication of the TLS.  Once this
draft goes to Proposed Standard I would recommend that the Telnet
Encryption option be moved to Historical.  But until that happens we
need it on the standards track.  

These drafts have been floating around the net for almost eight years
with many implementations.  Its time for them to move on.

- Jeff

    Jeffrey Altman * Sr.Software Designer * Kermit-95 for Win32 and OS/2
                 The Kermit Project * Columbia University
              612 West 115th St #716 * New York, NY * 10025
  http://www.kermit-project.org/k95.html * [email-masked]

---

From: Harald Tveit Alvestrand <[email-masked]>
Date: Wed, 24 Nov 1999 08:02:49 +0100

>divergent.  If 3DES is a better PRNG than DES then it is stronger.

Indeed. Or rather: If draft-altman-telnet-enc-des3-[cfb,ofb] describes a 
mechanism where the best known attack is (significantly)more difficult than 
the best known attack on draft-tso-telnet-enc-des-[cfb,ofb], it should go 
to Proposed Standard (and the shoe is on the other foot; the -des- ones 
shouldn't go forward to Proposed, since DES-protected data is known to be 
vulnerable to brute force attacks).

>drafts to go to Proposed Standard.

I'm not at the moment questioning whether draft-tso-telnet-encryption-04.txt
should go to Proposed; the question hasn't been raised.
I'm questioning the arguments for letting 
draft-altman-telnet-enc-des3-cfb-01.txt and 
draft-altman-telnet-enc-des3-ofb-01.txt should go to Proposed.

>with many implementations.  Its time for them to move on.

If it is possible to satisfy RFC 2026 para 4.1.1:

    A Proposed Standard should have no known technical omissions with
    respect to the requirements placed upon it.  However, the IESG may
    waive this requirement in order to allow a specification to advance
    to the Proposed Standard state when it is considered to be useful and
    necessary (and timely) even with known technical omissions.

Yes.

                      Harald

--
Harald Tveit Alvestrand, EDB Maxware, Norway
[email-masked]

---

From: Harald Tveit Alvestrand <[email-masked]>
Date: Wed, 24 Nov 1999 08:02:49 +0100

Yes.

                      Harald