Significant region based robust watermarking scheme in lifting wavelet transform domain

With the aim of designing a more robust digital watermarking scheme against various unintentional and intentional attacks, a significant region (SR) based image watermarking technique is proposed in the present paper using lifting wavelet transform (LWT). While the energy compaction property of LWT provides higher tolerance against image distortion as opposed to conventional wavelet transform, the proposed block selection procedure provides greater security over the existing watermarking approaches. Non-overlapping coefficient blocks from the lowpass subband are selected after applying three levels of LWT and using certain criterion based on minimum coefficient difference and a threshold value. To disguise the intruder completely, secret key based randomization of coefficients, blocks, and watermark bits is incorporated. Maximum coefficients difference of each selected block and the same threshold value are then used for deciding which block to choose for embedding the bit 0 or 1. Performance of the proposed method is analyzed and compared with some of the existing schemes that demonstrates that the proposed scheme not only outperforms other methods with respect to various attacks for most of the cases, but also maintains a satisfactory image quality.