Semi Fragile Watermarking for Content based Image Authentication and Recovery in the DWT-DCT Domains

Content authentication requires that the image watermarks must highlight malicious attacks while tolerating incidental modifications that do not alter the image contents beyond a certain tolerance limit. This paper proposed an authentication scheme that uses content invariant features of the image as a self authenticating watermark and a quantized down sampled approximation of the original image as a recovery watermark, both embedded securely using a pseudorandom sequence into multiple sub bands in the Discrete Wavelet Transform (DWT) domain. The scheme is blind as it does not require the original image during the authentication stage and highly tolerant to Jpeg2000 compression. The scheme also ensures highly imperceptible watermarked images and is suitable in application with low tolerance to image quality degradation after watermarking. Both Discrete Cosine Transform (DCT) and DWT transform domain are used in the watermark generation and embedding process.