A Cloud-based Transcoding with Partial Content  Protection Scheme 
Rizwan Shah, Muqaddas Hashmi, Mamoona Asghar, Martin Fleury
Journal of Information & Systems Management, Vol. 6, No. 4, 2016.
DOI: 
Link: http://www.dline.info/jism/fulltext/v6n4/jismv6n4_2.pdf
Abstract:
Multimedia content is now routinely distributed between devices across global networks. These devices differ in their video rendering capability in terms of frame rate, quality, and spatial resolution. To facilitate content exchange between such devices it is necessary to transcode the video format; otherwise no exchange can take place. To prolong battery life on mobile devices, transcoding may take place remotely on a cloud data center and in which case content protection is advisable. This paper presents an effective multimedia content protection technique that removes the need to decrypt the video prior to transcoding. It does this by partially encrypting the compressed video in such a way that it is decoder-format compliant. The demonstrated scheme allows the transcoder to transrate the video to a desired bit-rate without spending time in encryption/ decryption before decoding the video. In this way, the content and decryption keys are not exposed to third party software at the remote cloud data center and there is no need for complex key management software at the cloud. Consequently, the proposed scheme significantly simplifies cloud-based processing compared to previous schemes.