| dc.description.abstract | In this thesis, a novel method is presented to hide secure data for secrete communications by incorporating cryptography and data hiding technologies. In our approach, original data is encrypted by using the order of a magic matrix with secrete keys. There are two fundamental operations, including substitution and permutation, in traditional encryption process. According to the selected host image and magic matrix, mapping table for substation and permutation sequence are generated instead of the fixed permutation rule and substitution table used in traditional encryption algorithms. There are three secrete keys, host image selection key and magic matrix selection key pair, for use in encryption and decryption processes for data transmission. Finally, secure data obtained from previous processes are hided into LSB bit plane of the host image to construct a stego-image.
The proposed system consists of two main modules, which are secure data hiding and data extraction modules. In data hiding module, eight steps are performed for data encryption and hiding. They are host image obtaining, magic matrix key obtaining, host mask generation, magic mask generation, mapping table generation, secure mask generation, secure data stream generation, and hiding process. As to the data extraction module, the first five steps are the same as those in the data hiding module excepting steps 6~8 which are secure data stream extraction, secure data stream decoding, and hiding data extraction.
Experiments were conducted on various binary images and gray images. The average Hamming distance, i.e., error bit rate, is about 50% between original data and error binary data extracted by any of the secrete keys which is error or the corresponding secure data is lost. The phenomenon reveals that any attacker can not extract correct data when any of the secrete keys is lost. In addition, the information extracted by the attacker using error key will be the same as that obtained by random guess. Experimental results demonstrate the validity and efficiency of our proposed method. Moreover, the advantages of image complexity and variability property are both considered in designing the robust secure data hiding algorithm. | en_US |