This book constitutes the refereed proceedings of the 9th IFIP TC-6 TC-11 International Conference on Communications and Multimedia Security, CMS 2005, held in Salzburg, Austria in September 2005. The 28 revised full papers and 13 two-page abstracts presented together with 4 invited papers were carefully reviewed and selected from 143 submissions. The papers are organized in topical sections on applied cryptography, DRM and e-commerce, media encryption, multimedia security, privacy, biometrics and access control, network security, mobile security, and XML security.