Guest Editorial: Special issue on privacy and trust management in cloud and distributed systems

W ITH the continuous drive towards availability of data and services anytime anywhere, privacy risks have significantly increased. We are now witnessing vast amounts of privacy-sensitive data being collected, sometimes unintentionally, in a myriad of different types of networks. Unauthorized disclosure, modification, usage, or denial of access to these data may result in high human and financial costs. In the distributed computing environments, trust plays a crucial role in mitigating such privacy risks by guaranteeing meaningful interactions, data sharing, and communications. When the actors (machine or human) in the networks do not know how to trust a piece of data or other actors, they can be either naïve or paranoid. The naïve actors will be exposed to privacy risks and security threats, whereas the paranoid actors will ignore opportunities and services otherwise available. Trust management is, thus, an enabling technology for security and privacy enhancement. While privacy preservation and trust management are already challenging problems, it is imperative to explore how privacy-oriented and trust-oriented approaches can work together and bring new solutions to protecting information sharing and critical cyber infrastructure. Furthermore, there are questions about whether existing trust models and privacy preserving schemes are robust against various types of malicious attacks. Privacy and trust can be meaningfully achieved only in the context of an application domain. Privacy and trust are playing critical roles in ensuring reliability, usability, and security of many emerging cloud and distributed system applications. Recent advances in cloud computing promise essentially an unlimited amount of resources to individual users, prompting a gradual migration of all types of personal digital content to the cloud. Social media networks, from collaborative projects like Wikipedia, blogs and microblogs like Twitter, to content communities like YouTube and social networking sites like Facebook, enable the creation and exchange of user-generated content and dramatically expand the information flow from enterprises to individuals. Smalland large-scale sensor networks, from global positioning systems, video surveillance networks, smart grid to the umbrella class of the Internet of Things, capture a wide range of analog information including locations, movements, appearance, power usage, grid stability,