[143272] in cryptography@c2.net mail archive
Re: UCE - a simpler approach using just digital signing?
daemon@ATHENA.MIT.EDU (Sascha Silbe)
Sat Jan 31 12:39:40 2009
Date: Sat, 31 Jan 2009 12:35:48 +0100
From: Sascha Silbe <sascha-ml-cryptography-metzdowd.com@silbe.org>
To: Ray Dillinger <bear@sonic.net>
Cc: cryptography <cryptography@metzdowd.com>
Reply-To: Sascha Silbe <sascha-ml-reply-to-2009-1@silbe.org>
Mail-Followup-To: Ray Dillinger <bear@sonic.net>,
cryptography <cryptography@metzdowd.com>
In-Reply-To: <1233352043.28107.143.camel@localhost>
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On Fri, Jan 30, 2009 at 01:47:23PM -0800, Ray Dillinger wrote:
> Each time Fred gives out his email address to a new sender, he creates=20
> a trust token for that sender. They must use it when they send him=20
> mail.
That's basically what I'm using, just without the digital signature=20
part: each person/organisation/website/whatever gets a different email=20
address for communicating with me (qmail makes this easy to implement);=20
mailing list and bugtracker addresses are filtered to accept only mail=20
with the correct headers.
It works much better than content filters, but it's basically limited to=20
1:1 communication (with a mailing list looking like a single entity as=20
it forwards traffic both ways). Most importantly, it breaks for CC=20
parties (*). Address lists on paper given out to a large number of=20
participants are problematic as well (those utilizing paper lists are=20
mostly non-tech-savvy - thus prone to attacks - and changing the address=20
is hard due to the long update interval of the list).
To get on-topic again:
Another scheme (that could be combined with the above one to solve only=20
the CC party problem) would be accepting only PGP mail and use a=20
manually updated whitelist / web of trust of PGP keys. Unfortunately,=20
PGP still isn't widespread enough to reject non-PGP mails and the ones=20
not using it are often far more susceptible to address harvesting=20
malware, limiting the usefulness of such a filter.
(*) CC party: group discussion without predetermined participants (so no=20
mailing list could be set up in advance)
CU Sascha
--=20
http://sascha.silbe.org/
http://www.infra-silbe.de/
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