Mozilla Persona is decentralized sign-in protocol. (Actually, the protocol is named BrowserID, but Mozilla rebranded their implementation to confuse everyone. It worked.) It uses e-mail-like identifiers and public-key authentication to validate identity assertions....
Passwords are everywhere. We have too many of them. We know we shouldn’t re-use them, but we already have too many and we can’t remember another one. So we use one in multiple places and we get in trouble when one website is compromised. They cost us time and money...