A highly robust two-stage Contourlet-based digital image watermarking method

• The first truly blind two stage watermarking method.
• We embedded signature in high and low frequency CT coefficients to increase the range of robustness.
• We embedded signature in local and global CT coefficients to increase the range of robustness.
• We efficiently embedded the signature to achieve low PSNR degradation of watermarked image.
• The proposed blind watermarking method achieves high robustness against wide range of attacks.

In this paper we propose a blind and highly robust watermarking method consisting of two embedding stages. In the first stage, the odd description of image is divided into non-overlapped fixed size blocks and the signature (watermark) is embedded in the high frequency component of the Contourlet transform (CT) of the blocks. In the second stage, the signature is embedded in the low frequency component of the global CT of the image. The main issue associated with two-stage blind watermarking is the selection of the less affected signature among the two embedded signatures. In this paper a measure is introduced to decide between the two extracted signatures. Simulation results indicate that the proposed method achieves higher robustness compared to other known watermarking methods. Moreover, since watermark is embedded in the local as well as global CT coefficients of two different frequency bands, the proposed method is robust against a wide range of attacks. This is due to the fact that most of the attacks affect either a specific frequency band or a specific location in the watermarked image.