This book constitutes the refereed proceedings of the 6th InternationalWorkshop on Security, IWSEC 2011, held in Tokyo, Japan, in November2011. The 14 revised full papers presented in this volume were carefullyreviewed and selected from 45 submissions. They address all currentissues in information and computer security such as foundations ofsecurity, security in networks and ubiquitous computing systems, andsecurity in real life applications. The papers are organized in topicalsections on software protection and reliability; cryptographic protocol;pairing and identity based signature; malware detection; mathematicaland symmetric cryptography; public key encryption.