Call for Discussion - Time-Delay Protocol

[stewarts at ix.netcom.com]

At 01:07 AM 10/23/96 -0700, project_31 at alias.cyberpass.net wrote:
>Very simply put, it is desired to put an encrypted, paragraph-length
>message into ubiquitous public distribution, contained in an explanatory
>plaintext.
>On a predetermined date stated in the plaintext, the passphrase is to be
>released and the parties holding the message may decrypt the cyphertext
>and know its contents.
[Threats: content-leaks, counterfeiting/spoofing, alteration]
>        1.  A large-modulus PGP public key is prepared prior to the
>            experiment and placed on (a) the keyservers and (b) at an
>            "authenticating" website of neutral interest and good
>            reputation.

This isn't enough - keyservers are NOT a substitute for the
Web Of Trust.  You probably need to have the authenticating key
signed by other well-known-in-the-target-community keys.
I don't know if you plan to use one authenticating public key
for future jobs, or use a different one each time; in the latter
case you'll also want to have a key to sign that one with.

>        2.  The critical message is encrypted conventionally (IDEA) in
>            ASCII format with a large passphrase and included in the
>            explanatory plaintext, which also includes the
>            authenticating key ID hexnumber and fingerprint, and
>            instructions on how to obtain the authenticating key.

Fingerprint is critical - otherwise you're subject to the "0xdeadbeef" attack.
You could also include the key itself in the signed message, if you don't
mind a bit of extra volume.

>        3.  The entire plaintext message is clearsigned with the
>            authenticating public key, and the resulting textfile is
>            widely distributed.


>        1.  How may this protocol be improved?
>        2.  What are the security flaws in this protocol?
>        3.  May this protocol be simplified without compromising
>            security?

The main alternative to PGP keys is Haber&Stornetta's "Surety" notary system -
they use trees of hashes to establish that a given document was 
authenticated at a given time, making the trees publicly available,
and the weekly master hash gets printed in the New York Times classifieds
weekly.
At minimum, you may want to notarize your PGP key that way.
        http://www.surety.com/


#			Thanks;  Bill
# Bill Stewart, +1-415-442-2215 stewarts at ix.netcom.com
# You can get PGP outside the US at ftp.ox.ac.uk
  Imagine if three million people voted for somebody they _knew_,
  and the politicians had to count them all.