TAKATSUKI is a rocky planet that lies within its star's habitable zone, but it has no atmosphere or native life.  It was colonized in the distant past because of its rich deposits of valuable rare elements.  The first settlers formed independent homesteads accountable only to themselves, but eventually they agreed to form a league that collectively controls the planet and limits immigration.  There are seven members of this league, which are called "Dōmei".  To ensure accountability to this regime, a cryptographically-secure identification scheme was established.  Any new arrival must broadcast their public key, and upon approval is required to join the least-populous Dōmei.  Failure to authenticate is punishable by death, and that sentence may be administered by any citizen.  Crime (such as killing an authenticated citizen) is adjudicated on the "Justice Channel", which transmits evidence for or against the alleged offense.  Each Dōmei gets one vote on whether to revoke the credentials of the accused, which is effectively a sentence of death unless the convicted person can quickly flee off-world.