Research On Information Hiding Based On PDF File

The object information hiding using is called cover, which can be divided intovideo information hiding, audio information hiding,image information hiding and textinformation hiding and so on. Although the video, audio and image contain moreredundant information which could be used for secret communication, as text files areused widely and frequently, the technology of information hiding based on text fileshas become a more important area in the research of information hiding in recentyears. Nowadays,there are many algorithms are based on plain text, Word, webfiles,etc. But information hiding algorithms based on PDF file is less. In this paper,information hiding algorithms based on PDF file are studied. The research work hasthe following main aspects:Propose a information hiding method based on the object properties of PDF file,and finished the design of the system on VC6.0.First,we convert the PDF file to PSfile, then we analyzed and studied the PostScript language which is a kind of pagedescription language, and found out the operator of the object’s coordinate. At last,the secret information will be embedded in the PS file and we converted the PS file toPDF file. In this process, we must follow the rule of coordinate precision. Thismethod changes the object’s position in the PDF file, but difficult to detect. Thisalgorithm does not affect the file reading and printing operations, and the embeddingcapacity is superior to similar methods. Compared with the methods based on thestructure of PDF file, this method makes up the gap of embedding capacity and ismore robust under the manipulations such as delete and addition.To enhance the embedding capacity and robustness of the information hidingalgorithm based on PDF file，a novel information hiding algorithm based on the objectof PDF file is proposed，and the design of the system on VC6.0is accomplished.Atfirst, a piece of PS code will be finished and added to PS file, this code will create anew object for PDF file, but this object won’t be detected even if we expand the PDFfor64times, then convert the encrypted information to attribute value of the newobject to hide it. This algorithm is robust under the manipulations of Adobe AcrobatProfessional9such as additions of notation, postil, stamp, signature, background,delete and addition. The experimentation shows this algorithm improved significantlyon embedding capacity and robustness, of course, it is highly transparent.