Research On Data Hiding Algorithms For BTC And VQ Compressed Images

Since 1990 s, with the rapid development of Internet, big data, cloud computing, communication and digital media technology, data hiding has become a research hot point in the field of information technology, especially in the field of information hiding technology. It is drawn more and more attention by governments, enterprises and academia. Data hiding is often used to conceal communication and used for digital watermarking(especially digital media content authentication). Concealed communication is often referred to as the technology, which is that the digital media, such as text, audio and video, etc. is used as the carrier, and the secret information is hidden into the digital media carrier, and then the hidden carrier is transferred via the public communication channel, especially the Internet, so as to achieve the aims of concealed communication. And digital watermarking is a kind of technology which can be used to authenticate the content authenticity and integrity of digital media. Digital watermarking can also be used to authenticate the ownership of digital media.Data computing, storage and analysis becomes more and more easily with the rapid development of modern information technology such as big data, Internet, cloud computing, etc. In spite of this, the bandwidth of network transmission is still a bottleneck. So the digital media such as images, audio and video, documents is required to be compressed to store and transmit for some applications, so that the data hiding technique faces the challenges of the compressed media.For digital images, the common compression and encoding formats are JPEG, block truncation coding(BTC), vector quantization(VQ) and fractal coding. BTC and VQ are the lossy compression technology based on image block encoding. BTC is often used to transmit image real time in that its advantage is low complexity, low memory space and high speed of encoding and decoding. VQ is used to store and transmit the huge image such as remote sensing image, meteorological image, radar image and military map in that its advantage is big compression ratio, simple decoding and less distortion. So, BTC and VQ have become a common compression encoding technology for some special areas.Based on this, several data hiding algorithms based on block truncation coding and vector quantization are proposed in this thesis.Firstly, a new data hiding algorithm using BTC quantization parameter is proposed, which can hide two bits of secret information in each image block. The hiding capacity is two times of the other algorithms while maintaining the quality of the image. The algorithm can be used for concealed communication while it can be used for image texture authentication because of its fragility.Secondly, an oblivious fragile data hiding scheme for images utilizing edge transitions in BTC bitmaps is proposed, which can hide one bit of secret information in an image block. And it can be used to conceal communication in that its hiding capacity is as much as other existing data hiding algorithms based on BTC.Then, a data hiding algorithm based on BTC compressed image block is proposed which utilizes the parity of extended inverse number of the adjacent image block boundary pixel gray value arrangement. The proposed algorithm can be used for image content authentication in that it is fragile for some attacks and image operations.In the end, a highly efficient lossless reversible data hiding algorithm based on two-stage VQ digital image is proposed, which can be used for concealed communication and image content authentication.In the thesis, the performance of the proposed algorithms is tested by many experiments, and the performance of the proposed algorithms is compared with other existing algorithms. For the data hiding algorithms based on BTC, considering of the index of PSNR and hiding capacity, the performance is tested and compared with several algorithms based on BTC. And the experimental results showed that the proposed algorithms are fragile for some attacks and digital image operations. They can be used for image content authentication. And because of their higher hiding capacity than other algorithms, they can be used to conceal communication. For the data hiding algorithm based on VQ, the performance is tested and analyzed with the indices of PSNR, hiding capacity, bit rate and transmission efficiency. And the results of the experiments show that the proposed algorithm can recover the original index table and the secret data from the bit stream. In that the data encoding and decoding process is reversible, so the two-stage VQ-compressed image can be recovered losslessly. The hiding capacity of the proposed algorithms is higher than that of other algorithms based on VQ. And the bit rate and transmission efficiency of the proposed algorithms outperform other algorithms based on VQ.