Blind Watermarking of Color Images Using Karhunen-Loeve Transform Keying

This paper presents a method for blind digital watermarking of color images. The proposed scheme performs a decorrelation of the RGB color bands of the image to be watermarked using a Karhunen-Loeve transform (KLT), then marks the coefficients of the KLT of the first band obtained. The novelty of the method resides in the fact that the KLT basis images used for the transforms are not related to the image being marked, but are from an image taken as the secret key used throughout the scheme. The watermarking of the chosen KLT coefficients is performed using an i.i.d. Gaussian sequence. The method shows good robustness to attacks and signal processing operations, in particular to JPEG compression, filtering, resampling and noise addition, maintaining at the same time a high image quality. In addition, the scheme is secure against protocol attacks such as copy attack and ambiguity attack.