We have recently hit this problem when designing a distributed solar powered proof-of-stake system. We are not sure how to keep the electricity that is produced tied to the actual person (as a producer) so that other people don't just come in and take over that person's equipment by force and steal the electricity produced. We realized that it has to do with a unique identity, and, protecting that. But we also want to keep it open system, open source, and op-out at any time.