Implementing Pseudonymity

I will give an overview of some technologies that enable pseudonymity - allowing individuals to reveal or prove information about themselves to others without revealing their full identity. I will describe some functionalities relating to pseudonymity that can be implemented, and some that cannot. My intention is to present enough of the mathematics that underlies technology for pseudonymity to show that it is indeed possible to implement some functionalities that at first glance may appear impossible. In particular, I will show that several of the intended functions of the UK national ID could be provided in a pseudonymous fashion, allowing greater privacy. I will also outline some technology developed at HP Labs which ensures that users’ personal data is released only to software that has been checked to conform to their preferred privacy policies.