From: "Robert A. Hayden" <hayden@krypton.mankato.msus.edu>
Date: Sat, 15 Jan 94 22:45:53 PST
To: Cypherpunks Mailing List <cypherpunks@toad.com>
Subject: Re: PGP posting validation
In-Reply-To: <9401160545.AA04896@toad.com>
Message-ID: <Pine.3.88.9401160001.A24751-0100000@krypton.mankato.msus.edu>
MIME-Version: 1.0
Content-Type: text/plain


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On Sat, 15 Jan 1994, Philippe Nave wrote:

> Here's my two cents' worth- how about a filter on incoming mail to the list
> that performs these functions:
>   1) check the incoming post for a PGP signature
>   2) If a sig is found, check it against the list's public keyring

	2a)  Make sure that as part of the sign up procedure, the 
		subscriber's public key is also provided.

>   3) If the key matches, pop a line like "X-PGP-Keycheck: user so-and-so"
>      into the posting
>   4) If the incoming message already has a "X-PGP-Keycheck:" line in it, 
>      drop that line off - somebody's trying to spoof us

also:
	4a)  Make sure the line pointing out that it was validated is part
		of the message, and not the headers, because some newreaders
		have a nasty habit of dumping headers that aren't recognized,
		or making them very difficult to find (you have to 
		remember to switch to full headers for pine, for example.)
		I would think that a line added to the end of the message
		as a trailer woudl work dandilly.

	5)  If there is no PGP signature, the message is bounced back to 
		the originating address.  Yes, this might bounce to a 
		non-existant one, but if joe@moron.com is trying to fake a 
		message from joe@foo.com, joe@foo.com would find out 
		about it then.  Also, make sure the reply-to: header is
		set so that messages bouncing due to a non-existant address 
		do lead to a loop.

> For those 'punks who can/will sign their messages, this would provide a simple
> 'reputation check' visible to all recipients. For others, postings would flow
> through the system exactly like they do today, vulnerable to spoofs and so on.

Of course, there is the question of the reliability of the automated 
reposter... :-)

> My main concern is that we get a filter online that is secure but simple.
> Programmers (myself included) will want to launch off and devise some 
> horrendously complex PGP empire right away, but it would probably be smarter
> to start small.

Keep it simple and functional, IMHO.

____        Robert A. Hayden          <=> hayden@krypton.mankato.msus.edu
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