UCAN Powered SSO

[QuinnWilton]

This is more of a stub than anything.

In an internal chat, @forgondolin brought up the idea of using UCAN to authorize connections to internal company systems. I liked the idea, and made the connection to Tailscale SSH, so this thread is just meant to act as a placeholder for exploring the idea of using UCAN as an SSO provider, in support of something like Tailscale.