A blind watermarking technique in JPEG compressed domain

We proposed a blind watermarking technique to embed the watermark in JPEG compressed domain. Low frequency DCT coeffi cients are extracted to form an M-dimensional vector. Watermarking is achieved by modifying this vector in order to point to the centroid of a particular cell. This cell is determined according to the extract ed vector, private keys and the watermark. A dual-key system is used to reduce the chance of the removal of watermark. An iterative approach is used to prevent the removal of watermark by JPEG re-quantization. Experimental results show that the watermark can be detect ed when the watermarked image is further compressed using a larger scaling factor.