Utilize Iterative Decoding Feedback Technique To Improve Spread Spectrum Image Steganography

• Main Authors: Huai Chang Wu, 吳懷璋
• Other Authors: Wen Thong Chang
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/56598971573349209041

碩士 === 國立交通大學 === 電機學院碩士在職專班電信組 === 94 === Information hiding is a comprehensive science which merges the disciplines of the cryptography, communication principle and digital signal processing etc. It can be categorized into Digital Watermark and Steganography base on its applications. The both scenarios embed data into carrier to achieve different task. The goal of digital watermark is protection of intellectual properties and mainly emphasizes robustness. Another purpose of steganography is covert communication and highlights invisibility. However, traditional cryptographic technique can’t fully satisfy the requirements for secret information protection. If transmit encrypted code may bring more attention especially under strict surveillance. At the mean wile, someone must hide secret messages into innocuous media to avoid suspicions by means of steangraphic techniques, therefore the sender and receiver could accomplish information exchange without even the spirits knowing about it. Our thesis is to improve the higher bit error rate of “Spread Spectrum Image Steganography-SSIS” proposed by L. M. Marvel et al. We discussed the hiding scheme of SSIS and brought up reasonable queries and testified our inferences by related experiments which help us to find the source of higher bit error rate of SSIS. We proposed two improvements that aim at this drawback, first approach preprocess the cover image before being embedded by adaptive wiener filter to decrease the variance of cover image and the second utilized iterative decoding feedback technique to estimate the channel then equalized the modulated signal in accordance with estimating results. After experiments, our techniques can decrease the bit error rate of SSIS significantly and maintain the fidelity of stego image. We also discussed the robustness of steganagraphic technique which was applied in spatial domain and took advantage of spread spectrum and error correcting techniques to protect hidden messages against the JPEG compression.