PGP posting validation

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As I recall, the PGP-filtered mail list idea was proposed to the list a while
back and semi-informally put to a vote. At the time, I 'voted' against the 
idea, because I did not perceive the spoofing problem to be serious enough
to warrant that sort of response. Times change, I guess - it's easy to filter
certain names and anon ids out of my mail, but more complex spoofs involving
SMTP ports and so on call for more involved filtering procedures.

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
  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

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.

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.

- -- 
........................................................................
Philippe D. Nave, Jr.   | The person who does not use message encryption
pdn@dwroll.dw.att.com   | will soon be at the mercy of those who DO...
Denver, Colorado USA    | PGP public key: by arrangement.

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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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