Abstract

Abstract There are various types of PKI that are widely deployed or have been proposed. They differ in the configuration information required, trust rules, and flexibility. There are standards such as X.509 [5] and PKlX [6], but these are sufficiently flexible so that almost any model of PKI con be supported. In this article we describe several types of PKI and discuss the advanta es and disadvantages of each. W e argue a ainst several popular and widely jeployed models as being insecure, unscalabge, or overly inconvenient. W e also recommend a particular model. lie term principul i s cominonly used in the literature for any client of the public key inlrastructurc (PKI), whether i t be h u m a n , server, client machine, or something clse. A principal i s anything that needs to authenticate itself or verify tlic identity of anothcr principal.