Compared with the Arnold transform,the image scrambling method based on bit shuffling pixels is much more secure,and has higher efficiency and speed.However,the key space of this bit shuffling pixels based method is too small to resist exhaustive search attack.Therefore,an improved method based on chaos is proposed in this paper.The security of the improved scheme is enhanced by increasing the number of the keys.Theoretical analysis and experimental results show that the proposed method is effective and has higher security.
Taking full advantage of the randomicity of chaotic system and its extreme sensitivity to the initial value, a new chaotic fragile watermarking algorithm is proposed. In the algorithm, the location key is looked as a logistic chaotic initial value for iteration to create a location matrix. According to this location matrix, a mapping image is generated and the embedding location of watermarking in image blocks is identified. Then, the watermarking sequence, which is related with the mapping image blocks and generated by H6non chaotic map, is embedded into the least significant bit （ LSB ） of the corresponding location in each block. Since the image content and watermarking are staggered, the algorithm has a higher security. Simulation results showed that the algorithm can detect and locate the tamper in watermarked images with an accuracy of 2 × 2 block pixels. At the same time, the watermarking images has good invisibility, and the original image is not required when extracting watermarking.
