Study On Data Hiding Techniques Based On Digital Image

With the rapid development and great popularity of Internet based modern communication technology, information share and transmission become more frequent and wide. However, it also brings us the information security problems, such as information theft, copyright protection of multimedia data and image authentication. It is difficult to solve the above problems purely by traditional security protection methods (e.g., cryptography). It has proved that data-hiding technique was a best solution to the security problem, thus forming a hot researching field in the world. Focusing on the issue of data hiding by digital image, this paper has accomplished the following research work.(1) We first analyze the general methods of image hiding in literatures, and then present a novel steganographic method in discrete cosine transform (DCT) domain. In order to improve the embedding capacity of a cover-image while maintaining the stego-image quality acceptable, the DCT blocks of a cover-image are classified into three classes based on human visual system (HVS) characteristics and fuzzy theory, and then the number of bits to be embedded in each quantized DCT coefficient of a DCT block is varied with the type of the block. The experimental results show that the proposed method performs better than the fixed-length least-significant-bits (LSBs) substitution method in DCT domain in terms of message capacity and image quality. Besides, the embedding data can be extracted from the stego-image without referencing to the original cover-image.(2) We describe an information hiding method in discrete wavelet transform (DWT) domain, which is compatible with the image compression standard of JPEG2000. The lifting scheme of integer wavelet transform algorithm is used for embedding operation. Based on HVS characteristics, the secret information is embedded in the middle frequency of sub-bands, so is robust to the general signal processing operations such as JPEG compression, high frequency filtering, and Gaussian noise during transmission.This research will shorten the distance between the image hiding theory and its practical application. It is of significance for secure information communication over Internet.