Research On Reversible Watermarking And Image Protection Techniques

With the boom of communication network and digital technology, digital multimedia has been widely used in many areas. Multimedia information can be easily intercepted, eavesdropped, copied, tampered, forged or deleted during dissemination and utilization, which could damage its confidentiality, copyright, integrity, creditability and availability. Therefore it is essential to find effective ways to deal with these problems. Multimedia consists of text, image, audio, video etc. My research mainly focuses on images as they are wildly used in our daily life. This dissertation will discuss it in details on how to protect the integrity, copyright and confidentiality of multimedia, and potential protection measures such as multimedia encryption, robust watermarking and fragile/semi-fragile watermarking.The first topic covered in this dissertation is reversible watermarking. Four different effective methods are proposed: 1) Since binary location map influences the valid payload dramatically, a more compressible location map is proposed. It increases the valid payload by reducing the the amount of auxiliary information. Experiments show it is effective to many existing reversible watermarking algorithms, which use the location map to distinguish watermarked pixels. 2) The existing reversible watermarking with the difference expansion only uses pixel pairs with small difference in row or column. A reversible watermarking using spatial quad-based difference expansion are presented, which makes best use of small differences in vertical and horizontal directions simultaneously to conceal information. Experiments show it can achieve more payload than the scheme using difference expansion at the same PSNR (Peak Signal-to-Noise Ratio). 3) A high data-capacity reversible watermarking without using location map is proposed. The host image is partitioned into 2×2 blocks. The blocks are stably sorted in rising order according to a smoothness measure. Choose suitable ones in that order, filter noise in them, and conceal information using the general difference expansion technique. 4) A more accurate predictor is proposed, and then a prediction-error expansion based reversible watermarking scheme is proposed. The scheme is superior to other similar ones.The second topic covered in this dissertation is an integrity authentication system based on reversible watermarking. If the image is tampered, it can detect the modification. Further more it can detect the tampered location and repair the modifications. If location is not tampered, then the host image can be restored completely without any loss.The third topic covered in this dissertation is multimedia copyright protection. The existing subsampling and DCT based watermarking schemes are not robust enough to noise contamination and lossy compression for threshold condition may be partially ineffective and watermarking information is concealed in different coefficient pairs with the uniform way. After reviewing the knowledge of watermarking system, a more robust adaptive method is proposed.Finally, Efficient and format-compliant JPEG2000 encryption schemes are propsed. Compared with text, image has some distinctive characteristics, such as huge size and high redundancy. According to these characteristics two format-compliant partial encryption schemes for JPEG2000 are proposed. The packets containing the coded bit stream of the magnificent bit plane of quantized coefficients are chosen for encryption. The 4 least significant bits of randomly selected bytes are encrypted by XOR or random circular shift operation. The schemes are efficient, compliant to JPEG2000, without influence of compressibility and can provide low and high security levels. They are more efficient than the similar schemes.