Research On Image Authentication And Data Hiding Algorithm Using Visual Perception

With the rapid development of the Internet and multimedia information processing technology since 1990s, the storage, modification, copy and transmission of the digital works via computers and Internet is becoming pretty easier and used more frequently. This causes the secure communication and authentication on digital works to face severe challenges. In recent years, as an effective resolution to the problems on image security, information hiding technique has become a hot research topic in information security field. A well defined information hiding system should have good robustness, transparency and security. To achieve good balance between robustness and transparency, an effective way is to exploit human visual perception, and then develop media adaptive data hiding algorithms. This dissertation focused on image adaptive data hiding and fragile watermarking technique by employing image natural features and visual perception characteristics. The main contributions of this dissertation are as following:1. A high-capacity image adaptive data hiding algorithm in spatial domain.Many existing steganographic methods hide more secret data into edged areas than smooth areas in the host image, which does not differentiate edges from textures and causes serious degradation in actual edge areas. To avoid abrupt changes in image edge areas, as well as to achieve better quality of the stego-image, a novel image data hiding technique by adaptive Least Significant Bits (LSBs) substitution was proposed in this dissertation. Firstly, the scheme developed an image visual perception model by exploiting the brightness, edges, and texture masking of the host image. Secondly, the algorithm used the visual perception model to estimate the number k of LSBs for data hiding. Pixels in the noise non-sensitive regions were embedded by a k-bit LSB substitution with a larger value of k than that of the pixels in noise sensitive regions. Moreover, an optimal pixel adjustment process was used to enhance stego-image visual quality obtained by simple LSB substitution method. To ensure that the adaptive number k of LSBs remained unchanged after pixel modification, the LSBs number was computed by first r most significant bits (MSBs) rather than all the bits of the image pixel value. The theoretical analyses and experiment results showed that the presented perception model could discriminate the edges from textures, and the proposed method achieves higher embedding capacity and better stego-image quality when compared with some existing LSB based data hiding methods.2. A visual perception based semi-fragile watermarking scheme in image spatial domain. In this scheme, the watermark was first generated by the hash of the image feature in Block Truncation Coding domain, and then was embedded into the host image with adaptive Least Significant Bit substitution. Finally, an optimal pixel adjustment was used to further enhance the transparency. The algorithm deduced theoretically the adaptive threshold for automatic tampering detection and location, and could differentiate automatically incidental attacks and malicious attacks. Experiment results showed that the proposed algorithm was sensitive to malicious attacks while robust to incidental attacks, and had good accuracy in detecting and locating tampered blocks. When compared to some existing semi-fragile watermarking methods, the proposed scheme achieved higher embedding capacity and accuracy in tampering location.3. An image adaptive semi-fragile watermarking based on wavelet transform.By taking full advantage of the visual perception characteristics and the local time-frequency characteristics of discrete wavelet transform (DWT), this dissertation presented an image-adaptive semi-fragile watermarking technique operating in DWT domain. The proposed algorithm embedded the watermark by modifying coefficients of the vertical and the horizontal detail sub-bands of image sub-blocks. The algorithm had good transparency, and the watermark was invisible to human eyes and adaptive to the original image characteristics because of the utilization of human visual perception. The experimental results showed that the proposed algorithm was effective and can distinguish adaptively some non-malicious image operations such as compression from malicious ones made on the watermarked image. The embedded watermark was sensitive to malicious attacks while robust to non-malicious attacks, especially to JPEG loss compression. Moreover, the scheme outperformed other semi–fragile watermarking algorithms at the classification of attacks.4. A lossless authentication watermarking based on adaptive arithmetic.Reversible watermarking schemes based on modulo-256 addition may cause annoying salt-and-pepper noise. To avoid the salt-and-pepper noise, a reversible watermarking scheme using visual perception characteristics and adaptive modular arithmetic was proposed. First, the high bits residual image was obtained by extracting r MSBs of the original image, and then the watermark strength and the adaptive divisor of modulo operation in each pixel were computed by employing the high bits residual image features. Finally, the watermark was embedded into different LSBs of original image with adaptive modulo addition. The original image could be lossless recovered if the stego-image had not been altered. Extensive experiments showed that the proposed algorithm eliminated the salt-and-pepper noise effectively, and the visual quality of the stego-image with the proposed algorithm had been dramatically improved over some existing reversible watermarking algorithms. Especially, the stego-image of this algorithm had 9.9864 dB higher PSNR value than that of modulo-256 addition based reversible watermarking schemes, on average.This dissertation provided new methodology and key techniques for image adaptive data hiding and semi-fragile watermarking algorithms. Research achievements in the paper will offer secure guard for secure image communication and image authentication via the Internet, and be help to promote the healthy and orderly development of digital media industry.