When designing and implementing a system that handles sensitive or valuable information, there can be few discussions that do not include some reference to ensuring adequate security. At a strategic level there will be high level requirements for security that will safeguard the system, which must ultimately translate to practical solutions and physical implementations. This chapter focuses on the technical implementation of security requirements and, in particular, the use of smart cards as trusted security tokens. In particular, it examines the significance of tamper resistance by exploring the different hardware and software platforms in relation to smart card attacks. It also highlights certain issues around the deployment of smart card technology in the financial industry.