With the development of GPS and 3G network, mobile navigation systems are widely used in people’s daily life. From 2D electronic map to 3D simulation map, the navigation services based on real-scene information is becoming the mainstream. Due to the rapid growth of mobile navigation systems, users are not satisfied with the""basic navigation services any more, such as locating places and devising paths. They put forward higher demands on location-based services (LBS for short). Thus, LBS applications based on mobile navigation systems has attracted more and more attention. This thesis studies the drawbacks and relevant technologies of LBS, then designs and implements the LBS application for mobile virtual navigation systems based on Android platform. First of all, it analyzes the current status of LBS services, and come up with a self-adapting individuation LBS proposal based on user interests. Secondly, according to the requirements of LBS functional integrity and type diversity, it designs three function modules of the LBS application, including Mobile LBS Module, Location Sharing Module and Designated Reconstruction of Real Scene Module. What’s more, Mobile  LBS Module is aimed to provide basic and extended location services to users, as well as user interest-based LBS information. Location Sharing Module puts forward a new check-in mode using physical medium, such as 2D barcodes and Bluetooth devices to share users’ current position. Designated Reconstruction of Real Scene Module is responsible for navigation route review and historical track queries, via the technology of SVG image compression and dynamic caching mechanism. Finally, the LBS application invokes Augmented Reality Module to show the location data, service results and navigation route in 3D form. The LBS application for mobile virtual navigation system based on Android platform in this thesis can provide navigation and location-based services of high quality directly and clearly, as well as bring users new experiences of mobile function. It has already achieved good results in experimental environment.

This thesis studies the Message Queue Telemetry Transport protocol (MQTT) as an application layer protocol in geographical location sharing applications using third generation cellular communication (3G). The MQTT protocol is compared in terms of energy efficiency and amount of data generated with the Hypertext Transfer Protocol (HTTP), which is currently used in typical location sharing applications. In order to compare the communication energy efficiency of both protocols a location sharing application prototype was developed for the Android platform. The application allows the use of HTTP and MQTT and was used to perform a number of experiments. The evaluation experiments show that MQTT is a good candidate as a protocol for location sharing. At comparable bandwidth and energy expenses MQTT offers better quality of user experience, since the subscribers are notified at once when the location of clients of interest has changed. The MQTT protocol is more energy-efficient than the HTTP protocol when the number of other uses with whom the client shares location is low and the location updates are frequent. The experiments also indicate that MQTT protocol is more energy-efficient than HTTP protocol in idle state, when there are no location information updates due to inactivity of all the clients, for example, if they are stationary. This is because MQTT client does not spend energy to poll the server for information updates.

Submitted by Izabel Franco (izabel-franco@ufscar.br) on 2016-09-06T17:28:27Z No. of bitstreams: 1 DissTAR.pdf: 2245231 bytes, checksum: 5abba91b1fd07f93123d5392b576f1ba (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-12T13:35:36Z (GMT) No. of bitstreams: 1 DissTAR.pdf: 2245231 bytes, checksum: 5abba91b1fd07f93123d5392b576f1ba (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-12T13:36:23Z (GMT) No. of bitstreams: 1 DissTAR.pdf: 2245231 bytes, checksum: 5abba91b1fd07f93123d5392b576f1ba (MD5) / Made available in DSpace on 2016-09-12T13:46:14Z (GMT). No. of bitstreams: 1 DissTAR.pdf: 2245231 bytes, checksum: 5abba91b1fd07f93123d5392b576f1ba (MD5) Previous issue date: 2015-03-23 / Não recebi financiamento / Mobile social networks are characterized by the sharing of user context information, such as the location of one’s mobile device, with one’s friends and groups of friends. The location information in a social network enables providers to offer products and services based on geographical area, which is considered either a personal gain or an invasion of privacy by the users who receive these offers. A user sharing location information with a particular friend or group of friends, without social network providers having access to this information, ensures the safety and privacy of the information. This paper presents a model of mobile social networking with privacy guarantees regarding sharing the location of members with groups of friends; it allows users to configure rules that determine to whom, when and where location information can be made available. The model provides three levels of privacy, chosen by the user, using techniques of anonymity and diffusion, which adjust the location to ensure the concealment of the information before it is made available on the social network. The proof of concept of the proposed model, called RSM Privacy, was developed for the Android platform. Performance tests showed that delays generated by the use of RSM Privacy are proportional to and justifiable for the privacy levels desired and chosen by users. A group of 50 users evaluated the model proof of concept, RSMPrivacy, with respect to usability and verified the efficiency of the techniques included in the proposed model. / Redes sociais móveis caracterizam-se pelo compartilhamento das informações de contexto dos usuários, como a localização de seus dispositivos móveis, aos demais usuários. A informação da localização em uma rede social possibilita que os provedores ofereçam produtos e serviços baseados na área geográfica. Alguns usuários, contudo, consideram essas informações como ganho pessoal, outros como invasão de privacidade. Por outro lado, o compartilhamento da localização de um usuário a um amigo particular ou a um grupo particular de amigos, sem que os provedores de redes sociais tenham acesso a essa informação com precisão, poderia garantir a segurança e a privacidade da informação. Neste trabalho é apresentado um modelo de rede social móvel com garantias de privacidade da localização de seus usuários a um grupo de amigos. Para tanto, permite configurar regras que determinam com quem, quando e onde a informação da localização pode ser disponibilizada. O modelo fornece três níveis de privacidade, escolhida pelo usuário, com o emprego de técnicas de anonimato e difusão/ajuste da localização que garantem a ocultação da informação antes desta ser disponibilizada na rede social. Uma prova de conceito do modelo proposto, denominada RSM Privacy, foi desenvolvida para a plataforma Android. Testes de desempenho evidenciaram que os atrasos gerados pelo uso do RSM Privacy são proporcionais e justificáveis aos níveis de privacidade desejáveis e escolhidos pelos usuários. A prova de conceito do modelo – RSM Privacy – foi avaliada por um grupo de 50 usuários quanto aos aspectos de usabilidade e foi evidenciada a eficiência das técnicas presentes no modelo proposto.

Location-sharing services have become increasingly popular with the proliferation of smartphones and online social networks. People share their locations with each other to record their daily lives or satisfy their social needs. At the same time, inappropriate disclosure of location information poses threats to people's privacy. One of the reasons why people fail to protect their location privacy is the difficulty of using the current mechanisms to manually configure location-privacy settings. Since people's location-privacy preferences are context-aware, manual configuration is cumbersome. People's incapability and unwillingness to do so lead to unexpected location disclosures that violate their location privacy. In this thesis, we investigate the feasibility of using recommender systems to help people protect their location privacy. We examine the performance of location-privacy recommender systems and compare it with the state-of-the-art. We also conduct online user studies to understand people's acceptance of such recommender systems and their concerns. We revise our design of the systems according to the results of the user studies. We find that user-based collaborative filtering can accurately recommend location-privacy preferences and outperform the state-of-the-art when training data are insufficient. From users' perspective, their acceptance of location-privacy recommender systems is affected by the openness and the context of recommendations and their privacy concerns about the systems. It is feasible to use data obfuscation or decentralisation to alleviate people's concerns and meanwhile keep the systems robust against malicious data attacks.

Smartphone users share their locations with location based services (navigation apps, dating apps, fitness trackers, etc.). These services can be useful, but introduce privacy concerns. Strategies have been suggested in academic literature to counter these location privacy issues while still maintaining some utility of the location based services. In practice, Google introduced a new location privacy protection mechanism in Android 12. Users are now able to share only their approximate location with any app that request their location. In this thesis, the Approximate Location feature in Android 12 is evaluated and tested in different scenarios (on device and simulated) to decide its potential benefits and drawbacks for a users location privacy. The source code analysis show that the Approximate Location feature uses a grid mapping (’snap-togrid’) technique to make locations less precise and adds a random offset to make it more difficult to reveal when a user crosses a grid border. Over longer time periods, an attacker can exploit the random offset to reveal a more precise location than intended. The random offset will change gradually, meaning a precise location can result in several approximate locations. By averaging the approximate locations that a stationary precise location generates over time, one could potentially create a new more precise location than the approximate ones. Simulations and some real world experiments on an Android 12 device show that this attack could be feasible, but that since the random offset only updates every hour the attack would be very time consuming. The simulations showed that when approximate locations were shared for one precise location 10,000 times (hours in practice), the mean approximate location was on average 478 meters away from the precise location, compared to 986 meters on average if the approximate location was only shared once. Analysis made on recorded and simulated locations show that even though the approximate locations use a grid with 2 km granularity, many public transport routes can be inferred. The success of unambiguously inferring a public transport trip using a users approximate locations depends on the length of the trip (the longer the easier) and on how many other public transport trips share the route or sub route of the trip (the more trips that share the route, the harder it is to infer the correct one). By combining historical approximate location data and public transport data, results indicate that 80.52% of the bus routes in the Region of Skåne in Sweden could be inferred if a user travels the full route. / Smartphoneanvändare delar sin platsdata med mobilapplikationer, s.k. ’location based services’ (LBS). Exempel på sådana applikationer är navigationsappar, dejtingappar och träningsappar. Dessa applikationer kan vara värdefulla för användaren, men leder även till ökade integritetsproblem. Teoretiska och praktiska metoder har föreslagits för att begränsa dessa problem utan att applikationernas funktionalitet drabbas i för hög grad. I praktiken så introducerades ett antal nya integritetsskyddande funktioner i Android 12 för att ge användaren mer kontroll över sin platsintegritet (location privacy). Nu kan användare välja att dela enbart sina ungefärliga platser till appar som efterfrågar deras platsdata. Denna funktion kallas ”Approximate Location” (ungefärlig plats). I denna masteruppsats undersöks denna funktion ur ett integritetsperspektiv, och testas i olika scenarion (både verkliga och simulerade). Detta görs för att avgöra funktionens fördelar och begränsningar när det kommer till användares platsintegritet. Källkodsanalysen visar att den den ungefärliga platsen genereras genom en ’snap-to-grid’ eller ’grid masking’-teknik som gör platsen som delas mindre exakt. Kortfattat kan det beskrivas som att världen delas upp i ett rutnät med horisontella och vertikala linjer där användarens plats avrundas till den närmaste brytpunkt mellan två linjer. Dessutom flyttas platsen slumpmässigt mellan varje delning vilket gör det svårare för en angripare att avgöra när användaren rör sig mellan olika rutor i rutnätet. Simulationer och experiment på Android-enheter visar att ju längre en smartphone delar sin ungefärliga plats, desto mer avslöjas om den exakta. När ungefärliga platser som korresponderade mot en stillastående exakt plats delades 10 000 gånger och avrundades så var den avrundade platsen i genomsnitt 478 meter ifrån den exakta platsen. Detta kan jämföras med 986 meter i genomsnitt om den ungefärliga platsen bara delades en gång. Analys som utfördes med simulerad platsdata visar att även om positionerna genereras på ett rutnät med 2 kilometers avstånd mellan linjerna så kan resor med kollektivtrafik exponeras, trots att enbart ungefärliga platser delas. Hur enkelt det är att exponera rutten beror på hur lång resan är (ju längre desto enklare), och hur många andra rutter som liknar resan (ju fler, desto svårare). Baserat på simulerade ungefärliga platser längs kollektivtrafikrutter kombinerat med kollektivtrafikdata, indikerar resultaten att 80.53% av alla bussrutter i region Skåne kan exponeras om en person delar sin ungefärliga plats längs hela rutten.