Robust watermarking method for medical image in cloud environment based on DFT encryption

The invention discloses a robust watermarking method for a medical image in a cloud environment based on DFT encryption, belongs to the field of multimedia signal processing, and achieves the embedding of a robust watermark in an encrypted image. The method comprises the following steps: carrying out DFT transformation of an original medical image firstly, achieving the quick encryption of the image through the point multiplication with a two-value chaotic sequence in a transform domain, and carrying out the encryption of a two-value text watermark; secondly carrying out the DFT transformation of the encrypted original image, extracting a characteristic vector of the encrypted image, carrying out exclusive-or operation through the characteristic vector of the encrypted image and the encrypted watermark, embedding the watermark, and obtaining a two-value logic sequence; thirdly extracting and restoring the watermark; finally carrying out DFT calculation of the encrypted image, and decrypting the encrypted image into the original image. The method is the zero watermark technology. Because the watermark is embedded into the encrypted image, the watermark is protected, and the original image is also protected.