In the old days, all we needed to know was a telephone number of the person we wanted to communicate with. Today, there are fixed and mobile phone numbers, email addresses, instant messaging handles, VoIP user names, account names at dozens of websites, blog URLs, and more. The list keeps growing as new methods of communication and collaboration are invented and innovation proceeds with no end in sight.

Radical simplification is needed not just because all these identifiers and the passwords that go with them can't be remembered. It's also needed because this fragmentation holds back new applications that take advantage of the new communications cornucopia: unified posting and messaging, user-centric remixing of a variety of data streams, multi-technology presence and communications, and many others.

Recently, a number of bottom-up projects (such as LID, OpenID, SXIP, i-names) have sprung up to provide unified identification and authentication across a range of IP-based services. Internet-wide identity interoperability, enabled by the YADIS project, is becoming a real possibility and will turbo-charge the development of a range of compelling new applications. In this talk, Ernst provides a brief overview over these projects, explains how to take advantage of interoperable digital identities, and discusses a couple of innovative applications.