Block fragile watermark generation and authentication method based on chaos hash function

The invention discloses a chaotic hash function-based blocked weak watermark generating and attesting method, and the method uses original zero set image blocks, values of image sizes (M, and N), watermark subtag and secret key as express terms of the chaotic hash function to generate binary watermark blocks, scattering and encrypting watermark image generated by the binary watermark blocks according to spacial positions of an image blocks and then inserting the watermark image in the lowest position of image, and detecting and locating distortion by differential image. The invention uses the chaotic hash function constructed of composite nonlinear digital filter and uses the secret key as part of the express terms to generate binary watermark blocks, simple and having higher safety; and can effectively differentiate distortion between non-watermark part and watermark part of an image, and accurately locates the distorted positions of the non-watermark part, able to effectively resist attack of quantization and black box.