This book constitutes the refereed proceedings of the Second International Workshop on Security, IWSEC 2007, held in Nara, Japan, October 29-31, 2007. The 30 revised full papers presented were carefully reviewed and selected from 112 submissions. The papers are organized in topical sections on subjects including Software and Multimedia security, Public-key cryptography, Network security, E-commerce and Voting, Operating systems, and Security and Information management.