Data Hiding in Encrypted H.264AVC Video Streams by Code Word Substitution

Abstract

Digital video sometimes needs to be stored and processed in an encrypted format to maintain security and privacy. For the purpose of content notation and/or tampering detection, it is necessary to perform data hiding in these encrypted videos. In this way, data hiding in encrypted domain without decryption preserves the confidentiality of the content. In addition, it is more efficient without decryption followed by data hiding and re-encryption. In this paper, a novel scheme of data hiding directly in the encrypted version of H.264/AVC video stream is proposed, which includes the following three parts, i.e., H.264/AVC video encryption, data embedding, and data extraction. By analyzing the property of H.264/AVC codec, the codewords of intraprediction modes, the codewords of motion vector differences, and the codewords of residual coefficients are encrypted with stream ciphers. Then, a data hider may embed additional data in the encrypted domain by using codeword substitution technique, without knowing the original video content. In order to adapt to different application scenarios, data extraction can be done either in the encrypted domain or in the decrypted domain. Furthermore, video file size is strictly preserved even after encryption and data embedding. Experimental results have demonstrated the feasibility and efficiency of the proposed scheme.

Existing System

Few successful data hiding schemes in the encrypted domain have been reported in the open literature. A watermarking scheme in the encrypted domain using Paillier cryptosystem is proposed based on the security requirements of buyer-seller watermarking protocols. A Walsh-Hadamard transform based image watermarking algorithm in the encrypted domain using Paillier cryptosystem is presented. However, due to the constraints of the Paillier cryptosystem, the encryption of an original image results in a high overhead in storage and computation. Note that, several investigations on reversible data hiding in encrypted images are reported recently. The encryption is performed by using bit-XOR (exclusive-OR) operation. In these methods, however, the host image is in an uncompressed format. A robust watermarking algorithm is proposed to embed watermark into compressed and encrypted JPEG2000 images.

Proposed System

We propose a novel scheme to embed secret data directly in compressed and then encrypted H.264/AVC bitstream. Firstly, by analyzing the property of H.264/AVC codec, the codewords of IPMs, the codewords of MVDs, and the codewords of residual coefficients are encrypted with a stream cipher. The encryption algorithm is combined with the Exp-Golomb entropy coding and Context-adaptive variable-length coding (CAVLC), which keeps the codeword length unchanged. Then, data hiding in the encrypted domain is performed based on a novel codeword substituting scheme. a novel scheme of data hiding in the encrypted version of H.264/AVC videos is presented, which includes three parts, i.e., H.264/AVC video encryption, data embedding and data extraction. The content owner encrypts the original H.264/AVC video stream using standard stream ciphers with encryption keys to produce an encrypted video stream. Then, the data-hider (e.g., a cloud server) can embed the additional data into the encrypted video stream by using codeword substituting method, without knowing the original video content. At the receiver end, the hidden data extraction can be accomplished either in encrypted or in decrypted version.

Architecture