Efficient Digital Watermarking in DCT Domain

A more efficient robust watermarking algorithm based on DCT is proposed in this paper. The strength parameter of watermark in some approaches proposed is determined by experiments, we aim at establishing a mathematical model for hiding data in host image. By modifying the relationships between the selected middle-frequency coefficients and standard variance of DCT coefficients, watermark is embedded. Based on the Laplacian distribution model of DCT coefficients, two thresholds of embedding watermark are deduced according to the minimum mean squared error (MMSE) and maximum a posterior (MAP) estimate respectively. Watermark can be extracted without the original image. A one-way hash is constructed by the RSA method. Experimental results show that this watermarking method is robust to common image processing, and it own good transparent.