Research On Multi-carrier-based Text Steganography

With the rapid development of network and digital technology, the security of information has also faced with severe challenge. As the current research hotspots in the field of information security, information hiding technology provides good support for securely, imperceptibly and completely transmitting the information. Text steganography is one kind of text information hiding technology, which takes the text as the cover carrier for covert communicationThis thesis has made a relevant research on the text steganography and its main contributions are presented as follows:1.The current major research results are mainly to design the steganographic algorithm for a single text leading to large amount of changes in statistical characteristics of the cover text. Thus, this thesis proposed a steganography based on multiple texts and run-coding. The proposed method takes the synonyms appearing in the multiple texts as the cover carrier, and then encodes the synonymous words in frequency order and introduces the term of run. The values of the elements in a run will be flipped and the run length can be changed by synonym substitutions to implement the embedding of secret information. The positions of substitutions dramatically and evenly distribute in the runs from different texts while preserving the balance of forward and backward flipping the values of elements in runs. Experimental results and analysis show that this method has improved the security of the information transmission and enhances the ability of resisting detection attack.2.This paper brought forward a new text steganography method with hierarchical security resulting from the low security and capacity shortages of steganographic methods based on the single data. First, multiple types of data in the whole cover document were regarded as optional steganographic covers to build up a hierarchical security steganographic model upon the the steganographic security levels defined by taking the characteristics of different types of data and the steganalysis as evaluation criterions. Then, a security level was adaptively determined by the secret message length, and the secret message was embedded into the selected independent different types of data in a cover document with the help of the built model. Theoretical analysis and experimental results show that compared with the steganography based on single data, the proposed method has expanded the steganographic capacity and reduced the modifications of the statistic characteristics of a single type of data in the cover document when the same secret message was embedded. In conclusion the proposed method improves the security of the secret message.