Li, Hongjuan, (The George Washington University),” Privacy Preserving Friend Discoverym in Mobile Social Networks” (2016)

Li, Hongjuan, (The George Washington University),” Privacy Preserving Friend Discoverym in Mobile Social Networks” (2016), Advisor: Cheng, Xiuzhen

Mobile social networking has been increasingly popular with the explosive growth of mobile devices. By allowing mobile users to interact with potential friends around the real world, it enables new social interactions as a complement to web-based online social networks. Motivated by this feature, many exciting applications have been developed, yet the challenge of privacy protection is also aroused. This dissertation studies the problem of privacy preserving in mobile social networks. The authors propose different mechanisms for various privacy requirements.
The first proposed algorithm is a secure friend discovery mechanism based on encounter history in mobile social networks, which mainly focuses on the location privacy. By exploring the fact that sharing encounters indicate common activities and interests, the proposed scheme can help people make friends with likeminded strangers nearby. We provide peer-to-peer confidential communications with the location privacy and encounter privacy being strictly preserved. Unlike most existing works that either rely on a trusted centralized server or existing social relationships, the proposed algorithm is designed in an ad-hoc model with no such limitation. As a result, the proposed design is more suitable and more general for mobile social scenarios.

The authors also develop an efficient customized privacy preserving mechanism, which not only protects the privacy of users’ profile, but also establishes a verifiable secure communication channel between matching users. Besides, the initiator has the freedom to set a customized request profile by choosing the interested attributes and giving each attribute a specific value. Moreover, the request profile’s privacy protection level is customized by the initiator according to his/her own privacy requirements. The authors also consider the collusion attacks among unmatched users.

The proposed protocol guarantees only exactly matching users are able to communicate with the initiator securely, while as little as possible information can be obtained by other participants. To increase the matching efficiency, the proposed design adopts the Bloom filter to efficiently exclude most unmatched users. As a result, the proposed design effectively protects the profile privacy and efficiently decreases the computation overhead. The third work for this dissertation explores fine-grained profile matching by associating a user-specific numerical value with each attribute to indicate the level of interest. And the profile similarity is computed with a secure dot-product. While existing studies are mainly focused on leveraging rich cryptography algorithms to prevent privacy leakage, the authors consider a novel cooperative framework by mixing some random noise with the private data to preserve privacy. By carefully tuning the amount of information owned by each party, it is guaranteed that the privacy is effectively preserved while the matching result of two profiles can be cooperatively obtained. After giving an introduction of the basic mechanism, the authors detail two enhanced mechanisms by taking collusion attack and verifiability into consideration. With no expensive encryption algorithms involved, the proposed methods are more practical for real-world applications.