There is an intrinsic conflict between creating secure systems and usable systems. But usability and security can be made synergistic by providing requirements and design tools with specific usable security principles earlier in the requirements and design phase. In certain situations, it is possible to increase usability and security by revisiting design decisions made in the past; in others, to align security and usability by changing the regulatory environment in which the computers operate. This book addresses creation of a usable security protocol for user authentication as a natural outcome of the requirements and design phase of the authentication method development life cycle.