  OpenPGP, an IETF Proposed Standard based on PGP application, has its own
Public Key Infrastructure (PKI) architecture which is different from the one
based on X.509, another standard from ITU. This paper describes the OpenPGP
PKI; the historical perspective as well as its current use. The current OpenPGP
PKI issues include the capability of a PGP keyserver and its performance. PGP
keyservers have been developed and operated by volunteers since the 1990s. The
keyservers distribute, merge, and expire the OpenPGP public keys. Major
keyserver managers from several countries have built the globally distributed
network of PGP keyservers. However, the current PGP Public Keyserver (pksd) has
some limitations. It does not support fully the OpenPGP format so that it is
neither expandable nor flexible, without any cluster technology. Finally we
introduce the project on the next generation OpenPGP public keyserver called
the OpenPKSD, lead by Hironobu Suzuki, one of the authors, and funded by
Japanese Information-technology Promotion Agency(IPA).
