Privacy Preserving Information Sharing in Modern and Emerging Platforms

<p>Users share a large amount of information with modern platforms such as web platforms and social platforms for various services. However, they face the risk of information leakage because modern platforms still lack proper security policies. Existing security policies, such as permission systems and isolation, can help regulate information sharing. However, these policies have problems, such as coarse granularity, bad usability, and incompleteness, especially when new features are introduced. I investigate the security impacts of new features in web and mobile platforms and find design problems that lead to user information leakage. Based on these analyses, I propose design principles for permission systems that mediate how information should be shared in modern and emerging platforms, such as web and social platforms, to provide functionality with privacy preserved. I aim to design permission systems that only allow least-privilege information access. Specifically, I utilize program analysis and natural language processing to understand how applications use sensitive data and correlate these data with their functionality. With this understanding, I design schemes that ask for user consent about unexpected information access and automatically reduce overprivileged access. I provide guidelines for platform designers to build their permission systems according to respective adversary models and resources. In particular, I implement the new permission system for social platforms and Internet of Things (IoT) platforms that enable least-privilege information sharing. For the social platforms, I incorporate the primitives of Opaque handle, Opaque display, and User-driven access control (OOU) to design a least-privilege, user-friendly, developer-friendly, and feature-rich permission system. According to my study on Facebook, OOU can be applied to remove or replace 81.2% of sensitive permission instances without affecting functionality. For IoT platforms, I present a new authorization framework, SmartAuth, that supports user-centric, semantic-based authorization. SmartAuth automatically collects security-relevant information from an IoT application’s description, code, and annotations, and generates an authorization user interface to bridge the gap between the functionalities explained to the user and the operations the application actually performs.