Sufficient encryption based on entropy coding syntax elements of H.264/SVC

While much attention has been paid to securing the transmission of single-layer video, multi-layer scalable video also deserves consideration. This paper presents a sufficient encryption (SE) scheme for the H.264 Scalable Video Coding (SVC) extension that maintains the compression efficiency and the decoder format compliancy of the bitstream, without compromising its confidentiality. SE is achieved by applying encryption of carefully selected codewords or bin-strings of the Context-Adaptive Variable-Length Coding (CAVLC) and Context-Adaptive Binary Arithmetic Coding (CABAC) entropy coders respectively. The selection of exactly what to encrypt is what distinguishes this contribution from that of others. The performance of the scheme is tested on sequences with varying spatial resolutions, thus demonstrating the advantages of the scheme when compared to alternative techniques. These advantages include: minimal computational delay by encrypting partial data; no bit-rate escalation by keeping the compression ratio unchanged; and format compliancy of the bit-stream at the decoder. The detailed security and comparative evaluation of the scheme confirms that it is suitable for commercial, real-time applications. As there is a minimal increase in processing requirements, the scheme is highly suitable for video distribution to users who have subscribed to differing video qualities on end systems ranging from small handheld devices to those capable of high spatial resolutions and frame rates.