The Third International Workshop on Security (IWSEC 2008) was held at Kagawa International Conference Hall, Kagawa, Japan, November 25-27, 2008. The workshop was co-sponsored jointly by CSEC, a special interest group on computer security of IPSJ (Information Processing Society of Japan) and ISEC, a technical group on information security of the IEICE (The Institute of El- tronics, Information and Communication Engineers). The excellent Local Or- nizingCommitteewasledbytheIWSEC2008GeneralCo-chairs, MasatoTerada and Kazuo Ohta. This year, there were 94 paper submissions from all over the world. We would like to thank all the authors who submitted papers to IWSEC 2008. Each paper wasreviewedatleastthreereviewers.InadditiontothemembersoftheProgram Committee, many externalreviewers joined the review process of papers in their particular areas of expertise. We were fortunate to have this energetic team of experts, and are grateful to all of them for their hard work. The hard work includes very active discussion; the discussion phase was almost as long as the initial individual reviewing. The review and discussion weresupported by a very nice Web-based system, iChair. We appreciate its developers. After all the review phases, 18 papers were accepted for publication in this volume of Advances in Information and Computer Security.Intheworkshop, the contributed papers were supplemented by one invited talk from eminent researcherAlfred Menezes (the Centrefor Applied CryptographicResearch, The University of Waterloo). There are many people who contributed to the success of IWSEC 2008. We wish to express our deep appreciation for their contribution to information and computer securit