An approach to self-embedding document watermarking based on LZW algorithm

The growth in the internet has led to an increase in the proliferation of digital data like documents, videos etc. Digital watermarking is emerging as an effective means to protect the copyright of original users. In this paper, we propose a content independent self-embedding document watermarking scheme using Lempel-Ziv-Welch (LZW) algorithm. Character based self-embedding document watermarking techniques require seven bits per character for indexing Word based document watermarking eliminates this drawback but it depends on a dictionary for selecting the index of a sub-image. Incase of addition to the dictionary vocabulary the indices need to be updated, which is a drawback. Our proposed method eliminates these draw backs by using LZW algorithm for selecting the index of a sub-image. The proposed method can also be used for multi-lingual documents. The average number of bits required per character for watermark indices are also reduced when compared to the existing self- embedding document watermarking techniques. Also the proposed method minimizes the chances of extraneous detection and restoration failure due to tampering.