| Summary: | 碩士 === 逢甲大學 === 通訊工程所 === 92 === In thesis, we are mainly concerned with the study of image steganography. Steganography and digital Watermarking are two areas of research which are generally referred to as “information hiding”. Steganography studies ways to make communication invisible by hiding secret in innocuous message, whereas watermarking originated from the need for copyright protection of digital media.
In this thesis, based upon the DCT (discrete cosine transform), we propose a new image steganography scheme capable of concealing a piece of critical information in a non-critical host image (called cover-image). A key matrix and a weight matrix are used as secret keys to protect the hidden information. Given a DCT middle-frequency block of size , our scheme can hide as many as bits of data in the block by selectively modifying, at most, two quantized coefficients in the block. It is pointed out that the proposed scheme provides a higher security and maintains a higher quality of the stego-image than the previous DCT based schemes. Further, experimental results show that the proposed technique is also robust against the Joint Photographic Experts Group (JPEG) lossy compression.
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