From: Adam Back <aba@dcs.ex.ac.uk>
Date: Wed, 23 Oct 1996 15:05:50 -0700 (PDT)
To: project_31@alias.cyberpass.net
Subject: Re: Call for Discussion - Time-Delay Protocol
In-Reply-To: <199610230807.BAA14932@sirius.infonex.com>
Message-ID: <199610230205.DAA00785@server.test.net>
MIME-Version: 1.0
Content-Type: text/plain



<project_31@alias.cyberpass.net> writes:
> [Though I have posted this to the group four previous times, I have not
> seen it - or any replies to it - in my incoming cypherpunks list

Not seen it either.

> 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.
> 
> An undetermined number of persons and organizations would have a high
> pecuniary and reputational interest in...
> 
>         1.  Knowing the contents of the encrypted message before the
>             passphrase is publically released.

2048 bit PGP signatory key, long passphrase conventional encryption.
If you are doubtful of the entropy of the passphrase you could encrypt
with a second PGP public key signed by the first, and simply reveal
the secret key.

Post the message to cypherpunks via a nice long chain of mixmaster
remailers.  (Then you can't be coerced into releasing the key early).

>         2.  Counterfeiting both the explanatory message and enclosed
>             cyphertext to include their own content, then placing the
>             spoofed message into wide distribution as genuine, or
>             flooding the net with multiple spoofs.

Spoofing is difficult to prevent because anyone can repeat what you
are doing, publish a key, publish the explanatory text and encrypted
message, then post the decrypt key later.

>         3.  Discrediting the message by attacks on its protocol
>             integrity in terms of date of release, modification after
>             stated date of release and any other valid (or invalid)
>             objections that may occur to them.

With Tim May's BlackNet key, there were several after the fact
attempted spoofs of it, people publishing other keys with "BlackNet"
as the key id, as a kind of denial of service attack.

Getting a timestamp from a PGP timestamping service on the key, and
also having the encrypted message and explanatory text timestamped
before releasing it would help.  Then people couldn't spoof unless
they knew before hand what kind of topic your release would be about,
so that they could pre-sign a selection to pick from as a spoof.

Adam
--
print pack"C*",split/\D+/,`echo "16iII*o\U@{$/=$z;[(pop,pop,unpack"H*",<>
)]}\EsMsKsN0[lN*1lK[d2%Sa2/d0<X+d*lMLa^*lN%0]dsXx++lMlN/dsM0<J]dsJxp"|dc`