Consensus Actions in Cipherspace?

[Ray Dillinger]

Are there any good general cryptographic protocols for groups 
taking group actions by formal consensus or voting rules?

I'm thinking of a "distributed agent" that is empowered to do 
various things but which is activated only by a vote of its 
owners.  This would be like a "Robo-moderator" for a newsgroup, 
or a "Robo-Personnel Administrator" for a company's Board of 
directors, or a "Robo-Rater" for a restaurant rating website, 
or....

Crucial facts about a protocol that does the right thing would be: 

1) DOES NOT create any single priveleged user or machine. 

2) Resistant to denial-of-service attacks and attempts to 
   "stack the vote." (Requires user authentication)

3) No altered versions of the agent ought to be able to gather
   enough information to force an action as long as at least 
   the majority of agents are unaltered.

4) Once a consensus is reached, a majority of the agents acting
   together should be able to take whatever action is found
   even if the dissenters' agents don't cooperate with them.
   (a consensus reassembles a key?  But then that key can't 
   be used again, what's the next key?)

				Bear