A robust text digital watermarking algorithm based on fragments regrouping strategy

In this paper, an efficient robust text digital watermarking algorithm is proposed based on watermark fragments regrouping strategy. To enhance watermark robustness, the original watermark is divided into several ordered fragments with an order number firstly, and then these fragments are embedded into document characters redundantly. When some fragments are missed or changed by deleting and tamper attack, the algorithm can recover the destroyed fragment using other correct fragments with the same order number based on the vote strategy. Experiment results verify that the algorithm can achieve stronger watermarking robustness, greater watermarking capacity and better watermarking invisibility. Especially, not like existing methods, the order number of each fragment is not embedded at the expense of watermarking capacity but indicated by a hash function which utilizes the character UNICODE.