Robust copyright marking using Weibull distribution

For multimedia document, watermarking provides many advantages; however, its vulnerability due to attacks using signal processing methods offers challenge in designing robust techniques. This paper presents a novel method for enhancing robustness in copyright marking into mid-frequency discrete cosine transform (DCT) coefficients of an image. We establish that Weibull distribution suitably models mid-frequency coefficients well and use it for hiding copyright data. Our method is robust against JPEG compression attacks at both high and low compressions. Further, it is statistically undetectable in comparison to existing techniques of data hiding based on DCT coefficients. This is because it insignificantly affects the DCT coefficients of the stego image without compromising with data hiding capacity of the host image. Simulation result on Lena, Gibbon, Boat, and Peppers images illustrates that our algorithm offers lower bit error rate (BER) and higher peak signal to noise ratio (PSNR) leading to improved imperceptibility. Thus, it is useful in robust copyright marking.

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