Date: Fri, 1 Sep 1995 23:42:09 -0400
From: "David M. Oliver" <dave@newshare.com>
Subject: Re: secure transfer using skey
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On Fri, 1 Sep 1995, Rob Hartill wrote:

> Basically, skey involves giving challenges which result in a 
> one-time-password, so if I'm not missing something obvious, clients
> and servers can just pass these challenges back a forth inside HTTP
> headers, and send the rest of the information encrypted using the
> one-time-password.
> 
> the passwords never get transmitted over the net, only the challenges
> and encrypted data.

	This is not quite the way S-Key works from my reading, but
	"close enough". 

	It seems to me, though, that each user would have to have
	a relationship with each server, since the SKey "initial passwd"
	has to be given to the server "off-line" (this is how the 
	server can generate the intermediate phrase, and subsequently
	know what the client will return "one time").  Thus the user
	needs, in advance, a "relationship" -- off line -- with each
	server.

	Another issue is how a client can generate a sequence of
	one-time passwords that would be known to a server (since you'd
	certainly not want to prompt the user to enter the intermediate
	phrase for every hyperlink).

	I have been thinking about this, too, from a slightly different 
	perspective, and I find SKey very attractive (if you are willing 
	to force clients to adopt new/additional software).  The key,
	I think, is having a secure way to avoid this previous relationship 
	requirement.  We're trying to fit this into our software in such a
	way that there would need to be only one (prior) relationship, yet
	access to a "universe" of providers.  Our thinking is not beyond
	the "concept fits" stage, though.  

> I think the skey code is PD, so could be dropped into clients and
> servers.

	The actual "SKey" is copyright Bellcore but there
	are several versions extant that appear to be PD. 
	Also, Bellcore is sponsoring a "One Time Password" 
	proposal at IETF.

> I must be missing something, cos this is just too simple.

	Yes, and no.  :-)

dave

+------------------------------------------------------------------+
| David Oliver                                   dave@newshare.com |
| Managing Director-Technology                Newshare Corporation |
+------------------------------------------------------------------+