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Abstract
A combined scheme of watermarking and fingerprinting technologies for image copyright protection is proposed. Most previous watermarking algorithms embedded either a pseudorandom sequence or a visually recognizable pattern as a watermark into the original media. The present paper advocates that a practical watermarking system should combine these two types of watermarks for advanced copyright protection. First, the original image is decomposed by a three-level discrete wavelet transform. Then, a visually recognizable pattern is permuted by a key, key0. This is then expanded and embedded into one of the middle-frequency sub-bands. Next, key0 is also used to choose the random locations from the counterpart middle-frequency sub-band for constructing the fingerprint of this image. Under these circumstances, this scheme is suitable for large-scale use of watermarking aimed at simultaneous identification and transaction tracking for owners. Extensive simulation results show that the watermarked image preserves high fidelity, and the embedded watermark, together with the constructed fingerprint, could be perfectly extracted under attack-free conditions. In addition, the combined scheme is robust to common image processing operations, geometric distortion, collusion attack and composite attack.