A Format Compliant Framework for HEVC Selective Encryption After Encoding

The security protection of Ultra-High-Definition (UHD) video is facing grand challenges due to changeable application scenarios. The video business is highly dependent on the video format structure, which makes the format compliance of the encryption algorithm essential. Existing HEVC Selective Encryption (SE) algorithms are difficult to encrypt with format compliance while independent from the encoding, which limits their practical application. In order to realize the format compliant encryption on encoded bitstream, this paper first proposes a non-diffusion rule by analyzing the coding format specification of High Efficiency Video Coding (HEVC). Following the non-diffusion rule, a Bit Flipping (BF) method and a Bit Insertion-Deletion (BID) method are proposed based on the lower bound mapping of the bypass syntax element bit coding interval. Then, considering the various binarization methods and the correlation between syntax elements when decoding, this paper proposes the Validity Principle (VP) and Independence Principle (IP) of format compliant encryption. Focusing on the binary bits of the primary bypass elements in HEVC, the encryptability of them is analyzed in detail, and the corresponding format compliant encryption schemes based on BF, BID methods are constructed. Based on the above, a Format Compliance Encryption (FCE) framework after encoding is formulated. The flexibility, security, and adaptability of the framework are analyzed. Finally, through experiments from the aspects of format compliance, encryption speed, and perception effect, the proposed methods, schemes, and framework are format compliance while ensuring the basic performance and security requirements.