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 were selected for presentation as full papers. In addition to these regular presentations, the CMS conference featured for the ?rst time a "work in progress track" that enabled authors to report preliminary results and ongoing work. These papers were presented in the form of a poster sessionduringtheconference;anextendedabstractofthepostersappearsinthis proceedings volume. From all papers submitted to the CMS conference, the p- gramcommitteechose13 submissionsfor inclusionin theworkinprogresstrack. In addition to regular presentations, CMS 2005 featured a special session on XMLsecurity,containingbothcontributedandinvitedtalks.Thisspecialsession was jointly organized by Rudig ¨ er Grimm (TU Ilmenau, Germany) and J¨ org Schwenk (Ruhr-Universit¨ at Bochum, Germany). Their assistance in organizing CMS 2005 was greatly appreciated.