From: Phil Karn <karn@unix.ka9q.ampr.org>
Date: Thu, 15 Sep 94 11:39:29 PDT
To: adam@bwh.harvard.edu
Subject: Re: Running PGP on Netcom (and Similar)
In-Reply-To: <199409141543.LAA25195@bwh.harvard.edu>
Message-ID: <199409151822.LAA00459@unix.ka9q.ampr.org>
MIME-Version: 1.0
Content-Type: text/plain


This discussion is ridiculous. If you can crunch keys on your own
trusted machine, why not just run PGP there? Or at least the RSA
secret key operations?

I've been saying for a long time that there is a role for the latter
device.  It would hold your PGP secret key and do all RSA secret key
operations (signing, decryption) locally, taking requests from and
communicating the results back to hosts running PGP that do the rest:
RSA public key operations such as signature verification and
encryption, and IDEA encryption/decryption.

Ideally this device would be a smart card, but a small palmtop might
make a good prototype (except for speed). The big win is in much
better protection of the RSA secret key; it would never have to leave
the device, except perhaps in encrypted form for backup.

By plugging this device into a (possibly hacked) host you could use
your RSA key without risking all of the traffic you have ever
protected or will protect with a particular RSA secret key if that
particular host happens to be compromised.

But any traffic that passed through the hacked host would still be
compromised, as it would if the link between the secret key device and
the host were tapped.  There's simply nothing you can do about it.

Phil