Restoration in secure text document image authentication using erasable watermarks

Abstract

In this paper, we propose a new restoration method for electronic text document images using erasable watermarks. In restoration application, finding sufficient number of low-distortion pixels in a block to embed sufficient information bits and their blind detection is difficult. In the proposed method, an erasable watermark is embedded in each block of a text document image for restoration of the original character sequence. The embedding process introduces some background noise; however the content in the document can be read or understood by the user, because human vision has the inherent capability to recognize various patterns in the presence of noise. After verifying the content of each block, the original image can be restored at the blind detector for further use and analysis. Using the proposed method, it is possible to restore the original character sequence after multiple alterations like character deletion, insertion, substitution and block swapping. © Springer-Verlag Berlin Heidelberg 2005.