OpenID is a way to login to applications or resources using an existing account that acts as a identity provider. The Fedora project acts as an OpenID identity provider for anyone with a Fedora Account System account.
We have an OpenID provider running named FedOAuth.
When trying to log on to an OpenID enabled site, give
as URL. Example, if your FAS login is JohnDoe, you would enter JohnDoe.id.fedoraproject.org. If you are not logged in to FAS at this stage, you will be first taken to the FedOAuth login page. On the first login from each external site, you will be taken to id.fedoraproject.org and asked to approve the OpenID request.
Screenshots are here.
OpenID should work for all websites accepting OpenID login. We are looking for feedback and developers to improve the code. Send feedback to the fedora infrastructure list, #fedora-admin on irc.freenode.net or in a infrastructure ticket.
Ipsilon (was called FedOAuth) was written by Patrick Uiterwijk.
A good place to start learning about OpenID and FedOAuth would be this classroom.
The OpenID implementation was completely rewritten from scratch in 2013.
Persona support was added in 2014. The Mozilla Persona service was discontinued in November 2016, with Mozilla recommending that users find other options and not try to self-host persona.
Many thanks to User:Ricky for his explanations on IRC.