Subject: [Isms] DSSH - possible?

From: Juergen Schoenwaelder <[email-masked]>
Date: Wed, 6 Jul 2005 02:05:06 +0200

Hi.

Stupid question to the security experts: Will it be possible to invent
a datagram ssh (DSSH) in similar ways as it was possible to invent DTLS?

/js

-- 
Juergen Schoenwaelder		    International University Bremen
<http://www.eecs.iu-bremen.de/>	    P.O. Box 750 561, 28725 Bremen, Germany

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From: Eric Rescorla <[email-masked]>
Date: Tue, 05 Jul 2005 17:26:17 -0700

> a datagram ssh (DSSH) in similar ways as it was possible to invent DTLS?

Yes. Well, sort of.

SSL/TLS is purely a secure channel protocol. SSH is really a suite of
protocols. One of these is a secure channel protocol and the others
(e.g. remote login, SCP, SFTP, etc.) run on top of that secure
channel. You could certainly build a datagram capable version of SSH's
secure channel protocol, but this wouldn't necessarily get you what
you want, since you couldn't use e.g., SFTP without also building a
datagram-capable version of that, which starts to entail a very
substantial amount of reinvention.

-Ekr

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From: Juergen Schoenwaelder <[email-masked]>
Date: Wed, 6 Jul 2005 02:50:50 +0200

> substantial amount of reinvention.

I think DTLS was not invented to replace HTTPS and I doubt DSSH would 
be designed to replace SSH or SFTP. 

I was simply wondering whether a datagram version of SSH would be 
feasible so that UDP based protocols could leverage the SSH secure 
channel protocol and more important probably the authentication 
protocols running on top...

/js

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From: Sam Hartman <[email-masked]>
Date: Wed, 13 Jul 2005 17:13:36 -0400

One problem I see with dssh is that the authentication protocols take
advantage of the full reliable transport nature of the ssh transport.
Setting things up so that you had reuse of authentication would
probably involve allowing some services to require reliable transport
and others not to do so.

That seems complicated.