Conventional data hiding methods for PDF file insert a payload data by slightly modifying the position of characters in a document. Even if the changes are small, a certain degree of visual distortion is inevitably introduced to the PDF file. In this work, we propose a new data hiding method that splits the space value between characters. Specifically, a space value is split into two or more related values. Except for the first value which is reserved to store the corrective data, each of the related values encodes a segment of the payload data. When the PDF file is opened by a PDF viewer, the visual appearance is exactly the same as its original counterpart, i.e., complete quality preservation. To prevent direct observation of PDF file, access control is introduced by setting an owner password, which is a built-in function in the PDF standard. In the best case scenario, 38,160 bits can be hidden, while the observed file size increase is 12,776 Bytes.
- Complete quality preservation
- Data hiding
ASJC Scopus subject areas
- Safety, Risk, Reliability and Quality
- Computer Networks and Communications