It is our great pleasure to present the proceedings of the 9th IFIP TC-6 TC-11 Conference on Communications and Multimedia Security (CMS 2005), which washeld in Salzburg on September 19 21,2005.Continuing the tradition of p- vious CMS conferences, we sought a balanced program containing presentations on various aspects of secure communication and multimedia systems. Special emphasis was laid on papers with direct practical relevance for the construction of secure communication systems. The selection of the program was a challenging task. In total, we received 143 submissions, from which 28...