Secure Spread Spectrum Watermarking Algorithm Based on Chaotic Map for Still Images

In this paper, a chaos-based spread spectrum watermarking algorithm is developed in the DCT domain for still image. The most important feature of chaos is its sensitivity to initial conditions. This characteristic makes chaos has been used successfully for secure watermarking and encryption. In our algorithm, we use logistic map to produce pseudo-random sequence. We use the logistic map twice: one is to encrypt the embedded position and other to generate pseudo-noise sequence. The encryption to embedding position can prevent the watermark from removing ilegally, so the security can be improved better. We also use binary meaningful watermark image so that the contents of the watermark is known. The binary image is extracted without using original image. We have also tested robustness of the proposed algorithm against various attacks using common image processing (JPEG compression, cropping, resizing, and noising). Simulations have confirmed that this algorithm is robust against the typical attacks. The extracted watermarks still can be recognized visually.