Data Hiding in a Kind of PDF Texts for Secret Communication

In this paper, we present a novel steganographic technique for hiding data in a kind of PDF texts. We first point out the secret channels in a kind of PDF English texts, which are generated from documents that make the texts justified to occupy the full line width and position each character individually. In succession, we describe our steganographic system PDFStego in which several strategies are applied to improve security, such as making use of redundancy to complement security; constituting two chaotic maps to meet the Kerckhoffs principle and to prevent statistical attacks, and applying the secure hash algorithm to enable integrity service and blindly extracting service. Moreover, we define the embedding capacity of our system. PDFStego can be used to exchange sensitive data securely or to add copyright information to the PDF files.