| With the developments of computer software and hardware technologies, we can efficiently create, edit or store all kinds of digital multimedia, the efficiency and accuracy of information expression has been significantly improved. The technologies of internet and telecommunication facilitate the access or distribution of various information resources. Information processing, analysis, confusion, compression and other operations become a relatively simple process because of the powerful digital signal processing (DSP) technolog. Science and technologies provide human great convenience, but bring many potential information security issues at the same time, such as information disclosure, malicious tamper counterfeiting and copyright infringement etc. The repulicatable and data-huge characters of multimedia reduce the credibility of digital works. The malicious tampering and illegal distribution of digital information bring society and people’s lives many hazards. Over the years, the passive defence technologies based on traditional cryptography have been regarded as the main protection means. However, with the development of the growing diversity of attack methods, proactive attacking gradually becomes the major threat to information content security. How to verify and protect the multimedia information confidentiality, authenticity, integrity, how to effectively implement necessary security protections become important and urgent issues in information content security field.Focusing on information content authenticity and integrity, multimedia authentication is a kind of information security assurance technology which is different from cryptography technique, and can defense against intrusion actively. Being an important branch of multimedia authentication, image content authentication can not only detect tampering attacks, but also distinguish conventional image processing from malicious attacks on the mechanism. Over the last decade, digital image content authentication technique has been regarded as a hot research topic in information security field. A large number of image content authentication algorithms have been presented and play an important role in image content security and copyright protection. However, the researches and practices on image content authentication technologies are still in developing stage, most schemes have many problems such as security vulnerability, high computational complexity and so on. Following the research trends of image content authentication technology, this paper combines many key issues in the image content authentication study based on perceptual hashing and digital watermarking respectively, and proposes new authentication algorithms. The main research contributions and innovations are as follows:(1) Image Content Authentication TheoryTo acquire a comprehensive knowledge and understanding of digital image content authentication, this study starts from the multimedia information security attributes, introduces image authentication model based on perceptual hashing and digital watermarking respectively, and analyzes the characteristics of image content authentication systems and performance evaluation indicators. As well known, image feature extraction is the core step of a perceptual hashing algorithm. According to the different extraction methods, this section analyzes the perceptual hashing algorithms respectively based on images statistical properties, the character or relationship of DCT or DWT coefficients, image invariant properties in conventional image processing. Based on the characteristics of semi-fragile watermarking in image content authentication, this paper analyzes watermarking generation, embedding and detection methods of semi-fragile image watermarking in details. Finally, the characteristics and differences between the two algorithms are compared and analyzed. (2)Anti-JPEG Compressed Image Perceptual Hashing AlgorithmBy the theory of JPEG lossy compression, we know that the DC coefficients of DCT remain relatively stable in the quantization process. Generating image feature by these stable coefficients, this chapter proposes an image perceptual hashing algorithm which can effectively resist JPEG image lossy compression. The paper derives the principle of image feature extraction and the basis of certification threshold setting by mathematical methods, introduces the algorithm steps from feature extraction and hash generation stage, image authentication stage in details. The simulation results show that the algorithm is robust against JPEG compression, has the function of detecting and localizating malicious tampering, and has the ability to detect image mirroring, filtering and noise operations.(3) Image Perceptual Hash Algorithm Based on Target CharactersConventional image processing operations may affect the image quality, and may lead to changes in image scale, but generally will not change the shape of the image. However, the operations by image stitching, synthesis, replacement, integration and other forms of malicious tampering will certainly affect the shape of the images. There is essential difference between these two kinds of operations. Based on this theory, this section presents an image perceptual hashing algorithm based on target invariant characteristics, and these invariant features refer to the image shape. Using Hu invariant moments as image features description operator, the scheme calculates the weighted average of the HU invariant moments of the image and the conventional processed images. Select five invariant moments which are good at differentiating normal image processing from malicious attacks to generate hash. In authentication period, calculate the distance of two hash values to judge the matching degree of two images. Simulation results and analysis show that the algorithm can distinguish the conventional image processing and malicious tampering, and prove the robustness to conventional image processing and vulnerability to malicious attacks.(4) Approximate Reversible Semi-fragile Image Watermarking AlgorithmThe image authentication researches based on digital watermarking start earlier and the proposed algorithms are more mature. However, most schemes belong to fragile watermarking algorithm which may be fragile to outside unintentional interference and the embedded watermark images may prone to produce large degree of distortion. This paper presents a watermarking algorithm which is not only resistant unintentional interference to a certain extent, but also can nearly recover the original carrier image. Simulation results show that the algorithm can effectively hide the watermark information, hold the robustness to slight interference and vulnerability to malicious attacks.In summary, this paper made theory and algorithms research on theoretical framework of digital image content authentication, key technologies of image content authentication based on perceptual hashing and semi-fragile watermarking. The proposed algorithms, simulations and performance analysis in this paper have positive meaning to the research and application of multimedia information content security. |
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