Re: pgp keys

At 11:55 AM 4/4/96 -0500, Jack P. Starrantino   jpps@voicenet.com wrote:
>Is there a reliable method for obtaining the pgp public key for an
>arbitrary email address? [....] to obtain keys I do not have.

Reliable?  No; not everybody follows The One True KeyDistribution Method,
or even follows one-or-more of the popular electronic approaches, 
and not all keys that are distributed electronically are on the Internet,
though some of them may be on intranets or fido or uucp nets.

There's also the problem that the results are not unique.  If you look
at the MIT keyserver, http://www-swiss.ai.mit.edu/~bal/pks-toplev.html,
in the cluttered "Bill Stewart" namespace, you'll find several Bill Stewarts,
and you'll find many people have multiple keys for each email address,
especially after they've been in the servers a few years.

>I've caught some of the discussion on key servers, and noted some
>people's use of their signature, plan, or home page to distribute their
>keys.  Are some combination of these suitable today? 

There's a collection of keyservers that stay in sync with each other,
including the ones at pgp.mit.edu.  bal's http interface is a popular
way to access them, though there are others communications methods as well.
Some other people use finger; finger's really just a telnet to port 79
while sending a requested name and holding the connection up to wait for
replies,
but not everybody uses that either, and many host systems don't serve finger.
My work PGP address is available on my company's internal phone-book web,
and printed on my business cards, though I have now put it on MIT's server.

>Is there a parseable convention in use for extracting keys from
mail/finger/html?
Sure - the standard ASCII form that PGP extracts keys in is parseable by PGP.
(You have to be careful, when obtaining keys by mail/finger/html, that if you
get multiple keys, you do something appropriate, like split them up first.)
Unfortunately, Real PGP likes to ask you interactively if you want to add
the keys it found to a keyring, or whatever, but you could just feed it
some "Y"s on stdin to keep it happy.  The new PGP 3.0 stuff will have libraries
so it's much easier to build clean routines to do this rather than interact.

>My goal is to make encryption the default behavior on outgoing mail. I
>am not concerned about local security.

Good luck!  You'll probably have to prompt the user at least for
disambiguation, and possibly for methods for finding keys as well.

Bill Stewart writes:

| At 11:55 AM 4/4/96 -0500, Jack P. Starrantino   jpps@voicenet.com wrote:
| >Is there a reliable method for obtaining the pgp public key for an
| >arbitrary email address? [....] to obtain keys I do not have.
| 
| Reliable?  No; not everybody follows The One True KeyDistribution Method,
| or even follows one-or-more of the popular electronic approaches, 
| and not all keys that are distributed electronically are on the Internet,
| though some of them may be on intranets or fido or uucp nets.

It would be neat if individual Internet sites could run their own key 
servers in a distributed framework, using whatever protocol(s) they 
wanted to.  Finding someone's public key shouldn't be rocket science - 
if you already have their email address.  Checking the signatures might 
be, though ?

The pgp.net folks have established the convention of "keys.<domain 
component>.pgp.net", which lends itself to a simple algorithm along the 
lines of...

  Email address:
    martin@mrrl.lut.ac.uk
  Look for:
    keys.mrrl.lut.ac.uk.pgp.net
    keys.lut.ac.uk.pgp.net
    keys.ac.uk.pgp.net
    keys.uk.pgp.net
    keys.pgp.net

I'm not clear on whether it would be friendlier on the DNS to start 
with the least specific cases and move down to the most specific (i.e. 
reverse the order of the steps).  The latter would seem to result in 
less junk (NXDOMAIN responses) being kept by DNS servers which 
implement negative caching.

Keyservers might be reasonably be expected to speak a number of 
protocols ?  e.g. mail to "pgp-public-keys", finger, and perhaps a 
dedicated key lookup protocol ?

OK so we're lacking a mechanism for indicating things like which 
protocols/services a host supports, on which port numbers, etc...  
Perhaps it isn't even something we should be thinking about in relation 
to key servers ?  In any case, lots of new DNS RRs have been proposed 
which could handle the problem - but not implemented or deployed :-)

As a quick hack, I suppose the embedded URL scheme used by Netfind 
could be nicked and put to use for public key servers, e.g. in 
pseudo-Perl

  foreach (text record at keys.<domain>.pgp.net) {
    next unless /^kx-/;     # only interested in kx-<URL>
    s/^kx-//;               # toss Key eXchanger prefix out
    &do_something_with($_); # use resulting URL
  }

Do people have any opinions about these ideas ?  Obviously the DNS is 
going to be vulnerable to spoofing, so those URLs may be dodgy.  If 
we're checking the signatures aggressively this needn't be a problem, 
at least in relation to serving up public keys ?

If anyone knows of a forum where this stuff is being discussed, I'd 
appreciate a pointer.  Would be happy to set up a dedicated list if 
there isn't anything already.  FWIW, I don't seem to see any discussion 
on cypherpunks, coderpunks, spki, ietf-pkix, ietf-asid, ietf-ids, ... 
:-(

Martin