Hiding Information In Digital Images

The amount of the transformations on the Internet is increasing rapidly due to the growing multimedia and network technologies. The Internet provides a public and convenient channel for exchanging information; however, the security becomes a critical issue on the Internet. Specially, the illegal users on the Internet may retrieve, intercept, camouflage, or copy the information on transferring. Fortunately, the steganography technology provides practical solutions for exchanging secret message on the Internet. At present, information hiding technology play an more and more important role in government, military intelligence, financial systems, and the area of medical and health. It's also widely used in secret communications, digital copyright protection, e-commerce security, data integrity and reliability validation and so on.With the rapid development of digital technology, all kinds of information hiding tools and techniques become more and more mature. Some of them have entered the practical stage. But there are still many technical problems to be resolved.Focusing on the security of the information transmitted on the Internet, this thesis presents three data hiding schemes, which apply many technologies such as Least Significant Bits (LSB), Wet Paper Codes (WPC), and Magic Matrix. The first two data embedding schemes aim at good embedding quality. The stego images generated by the schemes are almost the same with their original images and achieve very high PSNR. Hence, the illegal peers on the Internet can not easily notice the secret data carried in the stego images. The third scheme inspired from the Sudoku use a magic matrix generated by a base-5 numeral system function to guide cover pixels' modification and fully explores embedding space in the magic matrix. This information hiding scheme gets very large embedding capacity with good security at the same time.