The Fifth International Workshop on Security (IWSEC 2010) was held at Kobe InternationalConferenceCenter, Kobe, Japan, November22-24,2010. Thewo- shop was co-organized by CSEC, a special interest group concerned with the computer security of the Information Processing Society of Japan (IPSJ) and ISEC, atechnicalgroupconcernedwiththe informationsecurityofTheInstitute of Electronics, Information and Communication Engineers (IEICE). The exc- lentLocalOrganizingCommitteewasledbytheIWSEC2010GeneralCo-chairs, Hiroaki Kikuchi and Toru Fujiwara. This year IWSEC 2010 had three tracks, the Foundations...