Persona

There aren't many decentralized authentication solutions out there. Namely, there are few alternatives to OpenID, and Mozilla Persona seems to be the most modern and most viable. Persona is based on the underlying BrowserID protocol. Further, Mozilla currently runs an Identity Provider (IdP) service at https://login.persona.org/ but one can run an IdP themselves, allowing for decentralization.

In terms of practical usage for sudo room, there are a sufficient number of libraries and plugins available for integrating and developing with lots of different applications and environments. This blog post from 2013 explains some more about how these libraries can be used.