PKI: Ten Years Later

This paper examines the history and evolution of so-called Public Key Infrastructure (PKI). It compares the original definition of PKI with a broader and more flexible definition that better reflects the variety of implementation philosophies available today. This current definition shows how the understanding of this technology has matured (although its essential characteristics have remained unchanged) and is derived, at least in part, from an evaluation and comparison of several quite different forms of PKI as well as a consideration of PKI criticisms over the years. The original definition of PKI may be dead or dying, but PKI technology continues to thrive as an extremely useful (and, in some cases, necessary) authentication solution.