A high level summary (and paraphrasing) of Zed Shaw’s talk at DEFCON 15 (in 2007) because I couldn’t find a good text version.
Utu is the Maori word for a system of revenge used by Maori society to provide social controls and retribution. Utu is also a protocol that uses cryptographic models of social interaction to allow peers to vote on their dislike of other peer’s behavior. The goal of Utu is to experiment with the effects of bringing identity, reputation, and retribution to human communications on the Internet. A secondary goal is wiping out IRC because apparently nobody really likes IRC.
The Utu project is now dead, but its source code can be found on Github. While reading this keep in mind that the core idea is a centralized chat server.
In order to have strong identity everyone has a cryptographic key, but because keys are so easy to create you have to be invited, and you have to have a handshake as part of the invitation because you need to care about who the invitee is. This doesn’t work if any jerk can invite any other jerk without consequence.