Over the past years, Public Key Infrastructure (PKI) technology has evolved and moved from the research laboratories to the mainstream, in which many organizations are now leveraging it as part of their core infrastructure system for providing and building security in their businesses. Understanding the challenges and requirements of PKI related operations through the sharing of case studies are critical to supporting the continued research and development of PKI technologies and related systems and applications to further progress and innovate for enhancing future development and evolution of PKI in the enterprises.

The International Workshop for Applied PKI (IWAP) is an annual workshop that was initiated in 2001 with the objective of focusing on research and application of Public Key Infrastructure. The first IWAP was held in Korea in 2001 with the active contributions and participation of Asian experts who shared valuable experiences on constructing PKI, in particular, on connecting PKI among Asian countries. The second IWAP was held in Taiwan in 2002, providing an opportunity for participants to exhibit and share their experiences in PKI construction. In 2004, Japan hosted the third IWAP workshop, further discussing the trend and issue on PKI-technologies.

The 4th IWAP workshop was held in Singapore on September 21–23, 2005, in conjunction with the 8th Information Security Conference (ISC'05) and the 1st Secure Mobile Ad-Hoc Networks and Sensors Workshop (MADNES'05). This is the first year for IWAP to have the formal proceedings published by IOS Press and available at the workshop. Selected papers in the IWAP'05 proceedings will be invited for submission to a special issue of the Journal of Computer Security.

A total of 43 submissions were received, of which the program committee selected 15 papers from 11 countries for inclusion in the proceedings. In addition, to enrich the workshop program, 3 valuable contributions originally submitted to ISC'05 were introduced into IWAP'05 program with the authors' consent. This workshop consists of one keynote speech and six technical sessions, covering the topics of PKI Operation & Case Study, Non-repudiation, Authorization & Access Control, Authentication & Time-Stamping, Certificate Validation & Revocation, and Cryptographic Applications.

This workshop was made possible only through the contributions from many individuals and organizations. We would like to thank all the authors who submitted papers. We also gratefully acknowledge the members of the Program Committee and the external reviewers, for the time and effort they put into reviewing the submissions. Special thanks are due to Ying Qiu for managing the web site for paper submission, review and notification. Patricia Loh was kind enough to arrange for the workshop venue, and takes care of the administration in running the workshop.

Last but not least, we are grateful to Institute for Infocomm Research and Microsoft Asia Pacific for sponsoring the workshop.

Jianying Zhou and Meng-Chow Kang – Program Chairs, Feng Bao and Hwee-Hwa Pang – General Chairs