This book constitutes the carefully refereed post-proceedings of the 6th Symposium on Foundations and Practice of Security, FPS 2013, held in La Rochelle, France, in October 2013. The 25 revised full papers presented together with a keynote address were carefully reviewed and selected from 65 submissions. The papers are organized in topical sections on security prools, formal methods, physical security, attack classification and assessment, access control, cipher attacks, ad-hoc and sensor networks, resilience and intrusion detection.