Research On Carrier-free Steganography Methods Based On Multi-keywords

The advent of the Internet has a significant impact on the way that people transmit information.At the same time,the security of information is suffering serious challenges.During the past two decades,the steganography methods have attracted more and more attentions as a protective method.Different from the encrypting methods,the steganography methods hide the secret information in multimedia carriers,so the third-party can't perceive the fact that the secret information is transmitted.Previous studies achieved by modifying the carriers can't effectively resist the steganalysis methods and attacks.To address this problem,carrier-free steganography methods have been proposed.These methods emphasize that no modification is carried in the carriers,and the stego-texts are generated from the normal natural carriers,so they are able to resist the existing steganalysis methods.The coverless information hiding method based on the Chinese mathematical expression can only hide single keyword,thus its hiding capacity is low.And there will be hidden tags extraction ambiguity in the extraction process.To solve these problems,an improved method named multi-keywords carrier-free text steganography method based on the Chinese character components is proposed in this paper.In the method,the hidden tags are selected from all the Chinese character components of words.And the POS is used for hiding the number of keywords.In addition,the redundancy of hidden tags in extraction process is eliminated by ensuring the uniqueness of hidden tags in every stego-text.The experimental results show that with appropriate hidden tags and large scale of text database,the proposed method can achieve that one text can hide 2.2 Chinese characters on average,more than 99%the success rate of hiding and over 90%the extraction accuracy on average.Meanwhile,the hidden capacity is improved to some extent relative to the single keyword method on the premise to ensure the success rate of hiding and extraction accuracy.By employing the characteristics of Chinese text,a method named multi-keywords carrier-free text steganography method based on Chinese Pinyin is introduced in this paper.In this method,a new type of hidden tag is proposed,that is the hidden tags are selected from all the Pinyin combinations of two words.Meanwhile,in the process of information hiding,a part of numbers of keywords can be hidden in the same texts,so that it can improve the hiding capacity and can improve the security of the algorithm.And in the process of retrieval,the way of joint retrieval starting from one combination can improve the time and space efficiency of algorithm.According to the above two methods,a carrier-free text steganography system based on multi-keywords is designed.The system can realize the functions of text pre-treatment,information hiding and information extraction.It doesn't need to modify the text carriers which has good performance in resistance to steganalysis methods.