Subject: [Simple] New draft on trust_path_discovery

From: Kumiko Ono <[email-masked]>
Date: Thu, 14 Jul 2005 00:00:26 -0400

Hi all,

Henning and I wrote up the I-D that proposes a mechanism to find friends
-of-friends and trusted domains, which could be used as a tool to 
protect users from spam/spit. We could not find any WG that this draft 
should belong to, but we believe the SIPPING/SIMPLE WG might be 
interested in this draft. Any comments are welcome.

>	Title		: Trust Path Discovery
>	Author(s)	: K. Ono, H. Schulzrinne
>	Filename	: draft-ono-trust-path-discovery-00.txt
>	Pages		: 14
>	Date		: 2005-7-12
>	
>   Chained or transitive trust can be used to determine whether incoming
>   communication is likely to be desirable or not.  We can build a
>   chained trust relationship by introducing friends to out friends, for
>   example.  We propose mechanisms for discovering trust paths and
>   binary responsive trustworthiness.  The trust paths are based on a
>   chain of trust relationships between users, a user and a domain, and
>   domains.  We apply this model to relatively low-value trust
>   establishment, suitable for deciding whether to accept communication
>   requests such as emails, calls, or instant messages from strangers.
>
>A URL for this Internet-Draft is:
>http://www.ietf.org/internet-drafts/draft-ono-trust-path-discovery-00.txt

Thanks,
Kumiko

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From: Jonathan Rosenberg <[email-masked]>
Date: Mon, 25 Jul 2005 17:28:27 -0400

This is a very interesting draft. This kind of presence-based reputation 
system is definitely a strong contender for a piece of the anti-spam 
puzzle.

Building a protocol to do this is very challenging. One of the design 
decisions is whether or not it is pushed based, akin to a vector routing 
protocl (as you have proposed) or whether it is query-based. I am 
concerned that a push-based routing protocol type of solution is simply 
not going to scale, as the level of aggregation will not be sufficient. 
Though there is a form of aggregation, in terms of combining paths to 
the same recipient, there is no way to aggregate decisions across 
recipients. The latter is analagous to combining prefixes in BGP, and 
that is not possible here since the identifiers are from a flat namespace.

Furthermore, I may not want to reveal all of my trust relationships to 
everyone, indeed, I may not want to reveal the same trust relationships 
to different people. Consider this example. I have a buddy list with 
lots of buddies on it. Those buddies include colleagues from work, 
family, and certain business associates that I deal with, but 
confidentially (example: the business development manager from a company 
about to acquire my company). I don't want everyone I trust to actually 
know that I trust this biz dev guy, since that reveals confidential 
information.

Because of this, I think that these trust chains need to be query based. 
Indeed, care must be taken to make sure the privacy issues I mention 
above can be dealt with. Indeed, if you allow transitive queries - user 
A queries B that queries C, it can get really hard to preserve the 
privacy needed.

Thanks,
Jonathan R.

-- 
Jonathan D. Rosenberg, Ph.D.                   600 Lanidex Plaza
Director, Service Provider VoIP Architecture   Parsippany, NJ 07054-2711
Cisco Systems
[email-masked]                              FAX:   (973) 952-5050
http://www.jdrosen.net                         PHONE: (973) 952-5000
http://www.cisco.com

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From: Henning Schulzrinne <[email-masked]>
Date: Mon, 25 Jul 2005 22:08:23 -0400

Thanks for the comments. I agree that scaling is going to be a 
challenge, although one has to be careful to compare distribution with 
local caching with queries in terms of overall efficiency. (This is 
something we have not done yet, unfortunately.) Unlike BGP routing data, 
these trust relationships are likely to be stable over very long time 
periods, measured at least in days or weeks, so that the total volume of 
information may not be all that large, particularly if one constrains 
the propagation. (This is the converse to BGP aggregation - you need to 
advertise every prefix that can't be aggregated, even if across ten AS 
hops, while long-haul trust relationships are probably of little 
interest. A friend ten links removed is not too meaningful.)

In general, if this type of trust path discovery is useful, it is likely 
to be useful for a somewhat enlarged group beyond one's own immediate 
acquaintances. I would expect to find most IETFers and networking 
faculty on my list of trust paths, but not a random teenager from New 
Zealand. Those strangers may just have to send me email first ("don't 
call me, I'll call you").

The problem with query-based protocols is to find the trusting parties, 
i.e., answering "who is trusting John Doe (who is sending me an IM)?". 
It would be very difficult to go ask all my friends and then have them 
ask their friends.

As to the privacy issues, I think the only viable solution is to only 
declare "public" trust, i.e., for people that one is willing to stand up 
  for in public, similar to the links in the various social network 
sites like Friendster. This will reduce the number of trust 
relationships, but for most people, I suspect that the large majority of 
"do I trust this person not to be selling aluminum siding" cases won't 
fall into the category of friends that need to be hidden from the world. 
This clearly needs more discussion in the draft.

Henning