Usenet - How to protect free speech?

From: Doug (
Date: 09/11/03

Date: Thu, 11 Sep 2003 22:35:41 +0800

I'm curious, I've just been having an argument with a bunch of guys
and I wondered if you people had some interest (and any suggestions
on other newsgroups to query if not...)

Basically it comes down to this:

There are a set of people P = {p1, p2, p3, ... , pN}. These
people want to have a conversation on the usenet networks.
However, there is an Evil Government Agency EGA that will arrest
these people because they talk about things with certain key words
in them.
I suggested that the people involved post using public key 
encryption, regularly rotating and posting an unencrypted public 
key to the newsgroup and privately distributing the newsgroup 
private key to members.
All posts are then public-key encrypted and can only be read by
people with the private key.
Then EGA can see that data is being posted but cannot access 
what the data being posted IS, and therefore, the posters are
Now, I've been challenged: If the set P is willing to add new 
members from the set of people who NOT in P, it becomes a trust
Any BAD new member added to P makes the private key available
to general use and the entire group is compromised.
So, what to do?
Can the usenet be used in such a fashion as to protect posters
from EGA's? If so, how? 
Am I completely on the wrong track here? Should I be looking at a
initial post service that strips incoming logs (but is vulnerable 
to EGA direct attack)?
CAN the usenet be used in such a fashion?