A watermarking with two signatures

A watermarking scheme is presented which embeds two different watermarks to the same frequency and extracts the marks with two different methods in the frequency domain. One of the two extraction methods needs a source image, whereas the other does not. Each extraction method uses a unique operation in extracting the watermark. The use of two watermark schemes is more effective in claiming rightful ownership. Furthermore, this watermarking is non-invertible and is robust against IBM attack as it obtains two different extraction results from the same image.