Mozilla's identity team has launched a new decentralized identity system aimed at replacing ad-hoc application-level authentication based on site-specific user-names and passwords.
The open-source experiment, called Browser ID, makes it possible for users to prove ownership of email addresses in a secure manner, without requiring per-site passwords.
A technical explanation is available:
BrowserID uses asymmetric cryptography and digital signatures to allow browsers to create signed assertions about the user's identity, and by identity providers to vouch (via signing of a key-email pair) for a user's identity in a disconnected fashion. BrowserID uses cross document messaging to communicate between documents served from different domains, which makes a usable implementation of BrowserID possible right now without modifications to existing browsers.
This video offers more details: