The global pandemic phenomenon has led to the evolution of the processes that allow the digital exchange of money and the regulations associated with it. The main purpose of this thesis is to design the development process of a digital payment mobile application. The result of this objective was obtained in collaboration with a Turin IT company operating in the world of digital payment solutions. My contribution to the project has concerned the drafting of the Security Analysis document and the implementation of Android modules that manage the user registration process for the mobile application. The thesis shows fundamentals factors to be considered during the software development process such as architectural patterns, actors involved, security requirements.