Research On Digital Image Authentication

Today, digital media has been applicated widely in every field. However, digital media can be tampered so easily that testify of authenticity and integrity has some practicality and theoretic meaning. Authentication technique based on digital fragile watermarking has gradually been one of the most important researches for its advantage in digital media authentication field.Some researches on image authentication based on fragile watermarking have been proposed in this paper. Which includes the scheme of watermark based on chaotic map, the secure and extract image authentication algorithm frame based on VCT (Values Combine Technique) and JPEG image exact authentication algorithm. The main research contents and originality of this paper can be summarized as follows:1. A kind of fragile watermark based on chaotic map is proposed, which combines the initial condition sensitivity of chaotic system with this watermark fragility. Experiment results show that fragile watermark is sensitive to tampering.2. One algorithm frame about secure and exact image authentication based on fragile watermark is presented. Analyses show this scheme can detect and locate tampers, and can resist against characteristic extraction attack and VQ attack (Vector Quantization counterfeiting attack), and brute-force attack against system is difficult.3. Because of the collision phenomena between the processes of the calculating and embedding watermark, we define some concepts, such as image error detect, block error detect, to describe reasonably the algorithm reliability, and proposing some design rules about reliable algorithm.4. With the widely application of JPEG image, we studied the exact authentication scheme of JPEG image in which select the embedding area by modifying quantification table, tradeoff between watermark embedding capacity and image quality. Experiments show this algorithm can authenticate watermarked JPEG image tempered or not effectively.At the end of this paper, we conclude our work and propose some future works.