The 5th International Workshop on Information Security Applications (WISA 2004) was held in Jeju Island, Korea during August 23-25, 2004. The workshop was sponsored by the Korea Institute of Information Security and Cryptology (KIISC), the Electronics and Telecommunications Research Institute (ETRI) and the Ministry of Information and Communication (MIC). The aim of the workshop is to serve as a forum for new conceptual and - perimental research results in the area of information security applications from the academic community as well as from the industry. The workshop program covers a wide range of security aspects including cryptography, cryptanalysis, network/system security and implementation aspects. The program committee received169 papersfrom 22 countries,andaccepted 37 papers for a full presentation track and 30 papers for a short presentation track. Each paper was carefully evaluated through peer-review by at least three members of the program committee. This volume contains revised versions of 36 papers accepted and presented in the full presentation track. Short papers were only published in the WISA 2004 pre-proceedings as preliminary versions and are allowed to be published elsewhere as extended versions. In addition to the contributed papers, Professors Gene Tsudik and Ross Anderson gave invited talks, entitled Security in Outsourced Databases and What does ‘Security’ mean for Ubiquitous Applications?, respectively.