Selective encryption and conditional access control for ROI scalability in scalable video coding

Abstract

In this thesis, we propose an encryption method to secure multiple regions of interest (ROIs) in bitstreams compliant with the Scalable Video Coding (SVC) standard. This allows protecting the SVC bitstreams from malicious attacks. We also propose a key generation scheme that facilitates efficient conditional access control to the protected ROIs. In order to successfully decode different ROIs, we identified three coding constraints that need to be taken into account: restricted or constrained motion estimation, restricted half-pel and quarter-pel interpolation at the boundaries of a ROI, and a restricted use of the Intra_BL mode at the boundary of a ROI. Further, in order to successfully apply encryption to the ROIs in SVC-compliant bitstreams, we also discussed a number of requirements that have to be met by the encryption technique used, such as preserving the spatial, temporal, and SNR scalability properties of an SVC bitstream, format compliance, and a low-complexity nature. Given a user’s condition such as the status of payment, the proposed scheme for conditional access control provides the necessary keys to access and decode various layers that belong to each ROI. The proposed schema can control the visual quality of each ROI, which may range from a very low to a very high quality. In this context, we also discuss a key generation scheme that limits the number of keys needed for encrypting and decrypting the different scalable layers that constitute the multiple ROIs in an SVC bitstream. Finally, a number of experiments have been conducted in order to verify the efficiency of the proposed methods. Our results show that the proposed schemes allow offering efficient and secure access to multiple ROIs in SVC-compliant bitstreams.