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Proceedings of the 2nd International Symposium on Information Processing (ISIP 2009)

Huangshan, China, August 21-23, 2009

Editors: Fei Yu, Jian Shu, and Guangxue Yue

AP Catalog Number: AP-PROC-CS-09CN002

ISBN: 978-952-5726-02-2 (Print), 978-952-5726-03-9 (CD-ROM)

Page(s): 75-78

Steganalysis Against Equivalent Transformation Based Steganographic Algorithm for PDF Files

        Shangping Zhong, Xin Fang, and Xiangwen Liao

Full text:  PDF


The equivalent transformation based steganographic algorithm for PDF files shows good performance, both in capacity and invisibility. In addition, data embedding by this algorithm need not change the size of a cover-file. However, a loophole exists in the steganographic scheme. Through analyzing the structure of a PDF file, we can reconstruct a PDF file by using the software tool according to the obtained “Creator” key, and reveal the presence of secret data. Furthermore, by making use of  the fact  that the residue sequence distributes uniformly, this paper’s steganalysis scheme can also estimate the  length of hidden data. To enhance security, in this paper, it is proposed to introduce a “random moduli” equivalent transformation based steganographic algorithm. It not only has more security, but also has larger capacity. Adopted practical PDF files, computing results show that this paper’s steganalysis scheme and “random moduli” equivalent transformation based steganographic algorithm are all effective. Moreover, it is possible to extend this paper’s methods to some other data sets, e.g., webpage structure text files.

Index Terms

Steganalysis, equivalent transformation based steganographic algorithm, reconstruction attack, random moduli, PDF file

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