A Novel Secure H.264 Transcoder using Selective Encryption

Abstract

In digital broadcast TV systems, video data is normally encrypted before transmission. For in-home redistribution, it is often necessary to transcode the bitstream to achieve optimum utilization of available bandwidth. If a signal is decrypted before transcoding and re-encrypted, this may lead to a security loophole. This paper presents a solution in the form of a novel H.264 selective encryption algorithm that encrypts sign bits of transform coefficients and motion vectors to allow secure transcoding without decryption. The performance of this system is compared with I-frame encryption. The results show that sign encryption is more secure than I-frame encryption and has a lower complexity. A hybrid system using a modified transcoder and sign encryption is found to give an optimal compromise between security and transcoding performance.

Secure transcoders for single layer video data

“…In many systems, standard compliance may be a desirable feature. In our earlier work, we proposed a system which encrypts only the intra prediction residuals in the I frames [9,13], thereby preserving all the header data. Since the entire frame is reconstructed using this information, the intelligibility of the frame can be destroyed while maintaining the standard compliance.…”

A Survey of H.264 AVC/SVC Encryption

“…4) Transcodability: Even if the bitstreams are not coded with SVC, the bitstreams can be transcoded via coefficient requantization and it is beneficial if this property is preserved in the encrypted domain [66].…”

“…The motion vector data are subject to further processing before entropy coding, i.e., motion vector prediction, which yields motion vector differences. The modification of motion vectors and motion vector difference data for encryption has been proposed frequently [36], [39], [30], [44], [74], [18], [28], [38], [42], [66], [37], [40], [62]. The schemes to modify the motion vectors and motion vector differences are diverse, e.g., many propose sign encryption [39], [74], [66], [62], while other encrypt the suffix of the exponential Golomb code [38], [40].…”

A new H.264 video encryption scheme based on chaotic cipher

“…Motivated by the specific requirements of video encryption, a variety of encryption algorithms have been proposed [1][2][3][4][5][6][7]. As a new standard, H.264 achieves higher compression efficiency and is expected to replace previous standard such as MPEG series standard within the next few years, the need for the secure copyright protection of H.264 video keeps rising which leads to a growing interest in the investigation of appropriate encryption scheme for H.264.…”