  Cloud storage plays an important role in social computing. This paper aims to
develop a cloud storage management system for mobile devices to support an
extended set of file operations. Because of the limit of storage, bandwidth,
power consumption, and other resource restrictions, most existing cloud storage
apps for smartphones do not keep local copies of files. This efficient design,
however, limits the application capacities. In this paper, we attempt to extend
the available file operations for cloud storage service to better serve
smartphone users. We develop an efficient and secure file management system,
Skyfiles, to support more advanced file operations. The basic idea of our
design is to utilize cloud instances to assist file operations. Particularly,
Skyfiles supports downloading, compressing, encrypting, and converting
operations, as well as file transfer between two smartphone users' cloud
storage spaces. In addition, we propose a protocol for users to share their
idle instances. All file operations supported by Skyfiles can be efficiently
and securely accomplished with either a self-created instance or shared
instance.
