In a military environment, tactical networks enable information sharing between all the different entities in the field. In this environment, multiple groups of people from different organizations, and with different goals and policies have to share information. The information has to be shared without the risk of leaking information to unauthorized entities. Cryptography algorithms are used to encrypt information with a key to remain in control of when, where and to whom it is shared. All information is encrypted based on the concept of content-based encryption. In this unreliable environment, the cryptographic keys used to secure the data have to be available to continue collecting and processing information.

A key management architecture should be in place, to facilitate the generation and distribution of these keys. The purpose of this key management architecture is to provide the entities in the field with specific keys such that information access policies can be enforced. The challenge here is that in tactical networks, network partitionings are expected to happen. Therefore, the same keys have to be redundantly available at multiple locations to prevent a single point of failure. In a connected network, the keys can constantly be synchronized between these locations. However, the problem of key de-synchronization occurs if the network is split for some time, keys are changed on both sides, and then the network is recombined. This leads to possible conflicting keys because synchronization was temporarily not possible. The key management architecture must be able to handle such conflicts and reintegrate them as necessary.

In this thesis, we present a decentralized key management architecture with a solution for the key de-synchronization problem. We propose to use Conflict-free replicated data types, to store the keys at multiple locations and prevent conflicts. Conflict-free replicated data types is a concept to store and replicate data across multiple instances. This data type is characterized by the possibility to update the data in all instances independently, and concurrently, without coordination between the instances. Additionally, three approaches for the coordination of key creation are proposed with different levels of consistency and availability. The architecture and the three approaches are compared in experiments to evaluate the differences and prove the feasibility of the designs. ... Read more

A start-up creates videos which users can watch to experience their running or cycling activity all over again. Currently, the company depends on external data sources to generate a video. To be less dependent on these sources the company wants to create their own tracking solution. This solution has to fit in their existing smartphone application available for iOS and Android. The company wants to remain flexible, therefore the tracking application has to be developed in such a way that it can also be used in other products the company might develop in the future. As a goal, the data has to result in visually pleasing videos for a large user base.

Based on an experimental app developed during the research phase, raw smartphone GPS data was found to be unsuitable for video rendering. To improve this data, a Kalman Filter is used, in combination with a smoothing algorithm. The system has been designed to allow code sharing between iOS and Android where possible. The system has been implemented in Objective-C, Java, and TypeScript. Separating the system in three blocks enables code reuse which improves maintainability of the system. The filter has been integrated as shared code in the TypeScript implementation, which allows filtering to happen on the device. The user of the React Native Module developed has freedom to retrieve the unprocessed and processed data.

The system has been tested by means of unit tests in all three programming languages used. Tests have been executed using a continuous integration server, testing each pull request against the current code base to ensure quality. Part of the testing phase includes the React Native Module to be implemented in the client's smartphone application to demonstrate its use. The application has been sent to a number of test participants to collect data from different routes and activities. The project can be seen as a success since all important requirements have been successfully implemented.
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