The Internet is more and more widely used as a way of communication in both personal and enterprise environments because it can solve the problem of long distances effectively and with low costs. The advanced mobile devices of today are capable of running a huge number of messaging services. Most of these services heavily rely on the stability and security of their servers, the mobile device itself is only a thin client.
The market share of Android powered smart devices is increasing. The main profile of this operating system is smartphones and tablets. Its use is just starting to grow in the field of smart accessories, televisions sets and head units of vehicles. Since it is one of the most widely spread operating systems in the field mobile devices today, applications developed for it can reach a large number of users.
First of all, the purpose of this thesis is to disclose the opportunities of Android based devices for coordinating a complex task. The chosen task for the application is reaching consensus. The description the consensus algorithms can also be found in the thesis.
Secondly, the thesis describes the necessary basics of cryptography, which are needed for the understanding of the protocols based on their algorithms.
Lastly, the thesis examines the development of an application providing safe, secure and advanced communication through the description of the design, implementation, testing and review of the system. The system avoids transmitting the messages for third party servers and it is also able to manage a special type of messages called events. These events can be useful for a team providing information infrastructures. During the downtime of the maintained servers the events can help them to coordinate their tasks without any dedicated server. The application implements a consensus algorithm to synchronize the list of users attending a particular event. Furthermore, the system provides functionalities of exchanging instant messages between users or groups.