ItwasourpleasuretoholdtheInternationalWorkshoponSecurity2006(IWSEC 2006) this year in Kyoto and to publish the proceedings as a volume of the Lecture Notes in Computer Science series. The workshop was our ?rst trial in that two major academic society groups on security in Japan, viz. ISEC and CSEC, jointly organized it; ISEC is a te- nical group on information security of the Institute of Electronics, Information and Communication Engineers (IEICE), and CSEC is a special interest group on computer security of the Information Processing Society of Japan (IPSJ). It was Ryoichi Sasaki, the...