Computer security is one of the most important current tasks in digital applications. However, from the best of our knowledge, there is little research for designing effective interfaces in the context of security management systems. Security problems for these systems include vulnerabilities, due to difficulty using the systems and poor user interfaces because of their security constraints. Nowadays, finding a good trade-off between security and usability is a challenge, mainly for user authentication services. This paper presents a preliminary process for designing secure and usable systems using a user-centered approach. According to the above, the researchers and development team could have a process for designing and carrying out security and usability solutions for users. For the development of this process, the MPIu+a methodology to implement highly usable and accessible interactive applications is used.