This book constitutes the thoroughly refereed post-proceedings of the International Workshop on Construction and Analysis of Safe, Secure, and Interoperable Smart Devices, CASSIS 2004, held in Marseille, France in March 2004. The 13 revised full papers presented were carefully selected during two rounds of reviewing and improvement. The papers are devoted to trends in smart card research, operating systems and virtual machine technologies, secure platforms, security, application validation, verification, and formal modeling and formal methods.