It also sounds very much like Kevin Marks’ Distributed Verification scheme using the rel=”me” attribute on web pages for which he built a chrome browser extension to actually implement it. Kevin also recently reported that Mastodon now actually supports this verification scheme in one of their most recent updates which should be used by instances that are regularly updating. The benefit is that this scheme already exists, is relatively well supported, there are parsers available for it, and it’s actually working on the open web. It’s also truly distributed in that it doesn’t rely on any central provisioning authorities that require ongoing maintenance or which could provide a monopoly on such a service.
Some more details about a proposed solution for MoodleNet that could solve some problems around decentralised identity.