Boosting robustness against composite attacks for quantization index-modulation algorithms

Abstract

Although solutions to a particular attack against the quantization index modulation (QIM) method such as valumetric scaling have been proposed, no attempt has been made to a combined form of common attacks, including valumetric scaling, constant change, additive white Gaussian noise (AWGN), and compressions. Of course, the composite attacks are more realistic but more difficult to solve. In this work, we tackle composite attacks in the framework of the QIM. We seek the solution in DC values of image blocks. By embedding watermark bits into DC values, QIM becomes generically robust against AWGN and most image compression attacks. To undo the alterations caused by valumetric scaling and constant change, pilot reference signals can be embedded into some selected image blocks, where the parameters for the affine transform model of the attacks are estimated directly from the watermarked images. Four versions of block-wise QIM algorithms with pilot signals are proposed. Experimental results show their robustness against severe composite attacks, including valumetric scaling, constant change, AWGN, and JPEG compressions.