JPEG Compression Factor Based Image Authentication Watermarking Algorithms And Their Performance Analysis

Digital image authentication watermarking aims to verify the integrality and authenticity of a host image. Cominbined with JPEG Compression Factor, this thesis studies the digital watermarking for JPEG image authentication. The purpose of this thesis is to improve the security and the performance of tamper detection.This thesis first summarizes the background of digital watermarking for JPEG image authentication. Three classical JPEG image authentication watermarking schemes, whose watermark data are embedded in the DCT, Wavelet and JPEG compression domains respectively, are selected and analysed. The weaknesses in these schemes are summarized. They are vulnrable to the collage attack, have a poor tamper detection performance and the lack of considering the JPEG compression factor.To adress above problems, this thesis proposes the image authentication watermarking algorithm combined with JPEG compression factor. This algorithm introduces the random correlations among the image blocks to resist collage attack and improve the security. And the tampering character of the eight neighborhoods of the image blocks and that of its mapping blocks is adopted to localize the fake regions and improve the tampering detection performance. Then, in terms of watermark embedding position and watermark capacity, this thesis analyses the correlation among watermark embedding position, invisibility and the capability of resisting JPEG compression, in which the correlation among watermark capacity, invisibility and tampering detection performance is also analysed. The simulation results indicate that embedding watermark in the LSB(Least Significant Bit) of the DCT coefficients corresponding to smaller quantization step in the quantization table can remit the conflict between the DCT coefficients to be protected and invisibility without dropping the capability of resisting JPEG compression. On the other hand, this thesis theoretically analyses the PFA(Probability of False Acceptance) and PFR(Probability of False Rejection) under general tampering and collage attack respectively, which are proved by the statistical experiments. As watermark capacity increases, the invisibility and PFR become worse with better PFA. At the end, this thesis expands the authentication watermarking scheme from gray images to the field of color images watermarking. The Y/U/V components are all used to generate and embed watermark to protect the three components. At the detection stage, the detection results of the three components are adopted comprehensively to localize the forged regions in the whole image. This algorithm provides superior localization result and betters the tampering detection result.In a word, this thesis aims to improve the security and. tampering detection performance. The authentication watermarking algorithms for gray images combined with JPEG compression factor and for color images based on the JPEG compression domain are proposed in this thesis. And the performance of the algorithms is analysed in depth to improve the capability for practical application of the algorithms.