| With the development of the information age, information security plays a more and more important role, in some cases, even threatens the safety of the country. Steganography belongs to the category of information security, and it transmits secret information which is embedded into carrier. Compared to encryption used more commonly, it is secure in transmission. JPEG is the most common picture formats. According to statistics,80% of Internet pictures are compressed by JEPG, so the research of steganography is of great significance to protect information security.Spatial domain steganography LSB and frequency domain steganography(Jsteg,F5,OutGuess and Yass) is analyzed and discussed, as well as their advantages and disadvantages. Then, the variant of Jsteg-JPM1 and its characteristic is introduced, and embedding process is converted into combination optimization problem. When solving combinatorial optimization problems, genetic algorithm has good global search capability, and simulated annealing algorithm has excellent local search capability, hybrid of them -GASA- has advantages of them and is able to obtain better feasible solution. GASA and JPM1 are combined into GASA-JPM1 to optimize embedded sequence and make smaller blocking feature of image after embedding.Carrier of steganography and large file steganography is researched. Selection of carrier, compression and coding characteristic of JPEG and characteristic of GASA-JPMl are discussed, and three selection standard, which has instructive sense in manual and automated selection. In order to improve the efficiency of large file steganography problem, the thesis studies carrier library in different forms r and the impact of segmentation algorithm. According to requirements, a feasible solution is given.Finally, to meet needs in daily life, large files steganography system based on GASA-JPM1 is implemented on MATLAB platform. Results show the system achieves the desired functionality. |
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