  In this paper, we propose a proxy system with JPEG bitstream-based file-size
preserving encryption to securely store compressed images in cloud
environments. The proposed system, which is settled between client's device and
the Internet, allows us not only to have exact the same file size as that of
original JPEG streams but also to maintain a predetermined image format. In an
experiment, the proposed system is verified to be effective in two cloud photo
steams: Google Photo and iCloud Photo.
