Information sharing and dissemination in the cyberspace have been widely deployed and applied in many fields, providing us flexibility, convenience, increased efficiency, and improved life quality. Advances in wireless communications and computing technologies enable people to create, share, download, and store the information more easily than ever before by the explosive popularity of internet-accessible smartphones and tablets, for its broad range of fascinating and useful mobile applications, like instant messaging, content sharing, and advertisement broadcast. It is observed that security and privacy issues have been greatly discussed on every aspect of information sharing that related to our daily life including social networking, healthcare, e-commerce, military, etc.;In this dissertation, we are along the line of security and privacy requirements for securing the information sharing and dissemination. First, we design a privacy-preserving multi-hop reputation system in Online Social Networks to enable users accumulate objective reputation for specific users via different friend chain. Second, for users with sharing purposes, they have to first establish trust relationships between each other. We investigate this issue and propose a trust-based privacy-preserving friend recommendation scheme which help strangers to establish multi-hop trust relationships in the cyberspace. Third, under the current network architecture, user interaction is performed and controlled by centralized platform, which largely deteriorate the scalability of it and further reveal all information to the service provider. To guarantee the authenticity and verifiability of information sharing, we develop a distributed privacy-preserving attribute-based authentication scheme for eHealth/mHealth system, which simultaneously provides the authenticity of patients' attributes and identities, but remains them undisclosed to unauthorized users. Inspired by the homophily phenomenon in social science, we leverage users' attributes for content dissemination. We propose a privacy-preserving social-assisted approach for information dissemination in Delay Tolerant Networks, in which the privacy of both information and the way of dissemination is well addressed. Then, we come up with a viable solution for tackling the privacy leakage during the friend search in Geosocial Networks. Finally, we design a revocable content sharing scheme for Geosocial Networks, which enables users to revoke the access right for their uploaded contents.
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