Research On Embedding Capacity And Efficiency Of Information Hiding Based On Digital Images

With the development of network technologies and digital devices, the digital data distributions become easy and fast. Message transmission over the Internet is very common in almost everywhere. Owing to the security flaws of the data communication channel, some problems may arise, such as copy violation, forgery and fraud. Therefore, the protection for digital data, especially for confidential information, becomes more and more important. As a kind of information security technique, digital steganography has been developed rapidly.Digital steganography based on images is a way of hiding the existence of secret message under the cover of a carrier signal in such a way that no one apart from the sender and intended recipient even realizes there is a hidden message. An original image, used to carry secret message as a carrier signal, is called the cover image. And an image which has carried secret message is called the stego image. By virtue of generating stego images that are perceptually identical to the cover images with small embedding distortion, the secret messages are embedded into the cover images.Generally, being an efficient information hiding system, what we want to achieve is the high embedding capacity of the cover image and the high visual quality of the stego image, high visual quality is also called embedding efficiency. The paper mainly studies on the information hiding technology based on gray scale digital images and especially considers the improvement of the embedding capacity and the embedding efficiency.For the current information hiding schemes, the improvement of the embedding capacity and the embedding efficiency is still the goal that we pursue and the starting point that we consider as to improve the algorithms. Considering the advantages and disadvantages of the previous methods, the paper proposes two algorithms for information hiding, one is high capacity of information hiding algorithm (HCIH algorithm), and the other is high quality of information hiding algorithm (HQIH algorithm). The main work is summarized as follows:Firstly, simply introducing the research significance about information security, analyzing the reason for putting forward information hiding technology and giving descriptions to some related conceptions about information hiding and information hiding based on digital images. Then, briefly introducing several common algorithms of information hiding based on digital images with their advantages and disadvantages. Finally, clearing the performance standard that one information hiding scheme may want to achieve.Secondly, considering the performance standard of embedding capacity, we present a high capacity of information hiding algorithm (HCIH for short), based on the (7,4) Hamming Code and the LSB replacement method, and inspiring from the "Hamming+1" method. The HCIH algorithm can be used to embed an email address as the secret message into an8-bit gray scale image, and achieves to embed twelve secret bits of the binary string of the secret message, which is converted from an email address, into a block of4x4cover pixels of a cover image sized512x512each time. Then we evaluate the validity of HCIH algorithm through experimental simulation. The experimental results show that our proposed HCIH algorithm achieves high embedding capacity (i.e.0.75bpp) and acceptable visual quality of the stego image, and can be used for the applications about large payload secret message transmission.Thirdly, considering the performance standard of embedding efficiency, we present a high quality of information hiding algorithm (HQIH for short), by introducing wet paper codes technology, for the purpose of improving the embedding efficiency. Considering that the embedding capacity may be lower because of introducing wet paper codes technology, when the embedding operation fails first time, the HQIH algorithm may try the second embedding operation to embed again by (7,4) Hamming Code oriented wet paper codes, to assure the embedding capacity. Meanwhile, the double operation also achieves higher security. Then, we evaluate the validity of HCIH algorithm through experimental simulation. The simulation experiments show that the HQIH algorithm achieves high embedding efficiency, that is the value of PSNR is more than52dB, and large embedding payload, that is the value of ER is between0.55bpp and0.83bpp, which can be used for different applications. Specially, our HQIH algorithm gives some degree of security by considering twofold safeguards.Finally, we give a summarization of this paper and present the next work.