The 4th International Conference on Security in Communication Networks 2004 (SCN2004)washeldatthe"DioceseHall"oftheArchdioceseofAmal?-Cavade' Tirreni and the "Armorial Bearings Hall" of the Archbishop Palace in Amal?, Italy, on September 8-10, 2004. Previous conferences also took place in Amal? in 1996, 1999 and 2002. The conference aimed at bringing together researchers in the ?elds of cr- tography and security in communication networks to foster cooperation and the exchange of ideas. The main topics included all technical aspects of data security, including: anonymity, authentication,...