We have designed and implemented a general and powerful distributed authentication framework based on higher-order logic. Authentication frameworks — including Taos, SPKI, SDSI, and X.509 — have been explained using logic. We show that by starting with the logic, we can implement these frameworks, all in the same concise and efficient system. Because our logic has no decision procedure — although proof checking is simple — users of the framework must submit proofs with their requests.
Andrew W. Appel, Edward W. Felten