Secure File System Services for Web 2.0 Applications Francis Hsu and Hao Chen We present a design for a file system that provides a secure file storage service for Web 2.0 applications. Currently, each Web application stores its own user data. This not only burdens the applications with storing, managing, and securing user data but also deprives users from controlling their own data. With recent proposals of secure client-side cross-domain communication mechanisms, we can provide an independent file system service to Web applications. This service returns the control over user data back to the users, where users can share or restrict access to their files as they wish, and relieves web application servers from the contractual or regulatory obligation of safeguarding user data.