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Nowadays, most networked mobile applications are built following a client-server architecture. In this paradigm, communications between devices are relayed through a centralized infrastructure. This technique has the disadvantage of requiring the presence of a centralized access point and depends entirely on it, which involves network delay and limits mobility. These limitations can be avoided by using an ad hoc model which allows direct communications between mobile devices.

Since ad hoc architecture is less widespread than centralized architecture, fewer resources are proposed for developing ad hoc applications. This master thesis presents the conception and the implementation of a library to facilitate the management of ad hoc networks amongst mobile devices. The library is implemented as a middleware component on the Android platform and is designed according to a layered model where each layer provides specific services. Bluetooth and Wi-Fi Direct technologies are used to establish ad hoc communications. Nevertheless, the main limitation of Wi-Fi Direct is that it does not support multi-hop communications. To overcome this limitation, the library proposes a hybrid approach by using Bluetooth technology to interconnect several Wi-Fi Direct groups. The proposed scheme provides an abstraction layer that handles multi-hop communications independently of the underlying wireless technology and uses the Ad hoc On-demand Distance Vector (AODV) routing protocol. All these mechanisms are encapsulated and are provided as high level APIs to manage ad hoc communications in a convenient way.

Finally, this master thesis provides several proof of concept applications which use the library, a brief performance analysis and gives a conclusion about the work accomplished as well as some suggestions of improvement.

ad hoc --- network --- mobile --- routing --- aodv --- android --- java --- bluetooth --- wi-fi direct --- Ingénierie, informatique & technologie > Sciences informatiques

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Today, almost everyone carries a mobile device, which is used for various purposes such as communicating with friends or watching videos on an online video sharing platform. However, it requires the presence of a centralised access point, which is not always available. This restriction could be avoided by transitioning to ad hoc wireless communications, where devices would communicate with each other directly. Even so, there are few resources available for the development of ad hoc applications. This master thesis presents the port of a Java mobile ad hoc library to Dart. Therefore, the ported library could be used by the Flutter framework, which allows to develop ad hoc mobile apps regardless of the mobile platforms used. Since the Java mobile ad hoc library is based on a layered architecture, each layer has been individually ported one by one. Another wireless technology, Bluetooth Low Energy, has been explored and used instead of Bluetooth Classic. Despite having a lower data rate, Bluetooth Low Energy is still used to overcome the limitation of Wi-Fi Direct, which is the non-support for multi-hop communications. Then, a new layer has been introduced and implemented, which is responsible for encryption and decryption of data. As a result, a key management system is needed and the on-demand self-organised public key management has been chosen and implemented for end-to-end secure communication. To provide secure communication beyond the end-to-end secure communication, the CRTDH group key agreement has been implemented and provides the possibility to have secure group communications. Study in the literature has shown that the symmetric cryptography ChaCha20 has proven to be very efficient in terms of computation time and energy consumption.

Ad Hoc --- Network --- Cryptography --- Flutter --- Dart --- Bluetooth Low Energy --- Wi-Fi Direct --- AODV --- Android --- Ingénierie, informatique & technologie > Sciences informatiques