Selective Encryption Algorithm for Highly Confidential Real Time Video Applications

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1. Introduction Conventional cryptographic algorithms, which are generally aimed at encrypting like text data (known as Naïve approach) not well suited for video encryption. This is due to the fact that conventional cryptographic algorithms cannot process the large volume of video data in real-time. Selective encryption of the H.264/AVC bitstream puts decoder to fully decode the encrypted video with degradation in video quality. This perceptual encryption has low encryption and decryption time. The video data are compressed to reduce the storage space required and to save bandwidth for transmission. Video compression removes redundancy, so that it is difficult to guess about a portion of a compressed bitstream to another. In addition,…show more content…
From an attacker’s point of view, brute-force attack may break the encryption of sign bit and level_suffix of the same length. Intra-prediction mode has only nine different values (0-8). Hence, the encryption of intra-prediction mode also has the threat of brute-force attack. So, the values of level_suffix with sign bits are encrypted with a higher length of bitstream (6 bits for luma and 4 bits for chroma), to reduce the threat of brute-force attack. However, this affects the compression bandwidth. We have also analyzed that without making motion vectors encryption, we can’t obtain temporal redundancy. Motion vector encryptions are proposed by several authors [4-9]. However, analysis shown in this paper said that 45-50% of motion vectors for each frame are not encrypted. Thus, a better encryption method is proposed at here in expense with compression bandwidth. Overall, we should create the balance between security and the increase in compression bandwidth. Four selective encryption methods are discussed here. A First method named ‘NZs in CAVLC’ encrypts level_suffix values with sign bits of up to three lowest frequency non-zero DCT coefficients in CAVLC encoding for all macroblocks. Second method named ‘NZs in CAVLC for I only’, which is same as the first method but encryption is done only in intra-coded macroblocks. Third method named ‘MV’

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