Secure watermarking scheme against watermark attacks in the encrypted domain

• We have proposed a robust watermarking scheme in the encrypted domain.
• For traditional schemes, original media could be exposed to the embedder.
• The robustness of watermark in the encrypted domain should be taken into account.
• We investigate the watermark attacks that can be performed in the encrypted domain.
• Our watermarking scheme would be helpful for copyright protection in the cloud.

The homomorphic cryptosystems create a great opportunity for secure signal processing (SSP). Watermarking in the encrypted domain provides a promising solution to the security of watermarking. However, the robust performance of the watermarking scheme in the encrypted domain should be carefully considered. In this paper, we propose a robust watermarking scheme in the encrypted domain, which protects the original images from the third party embedders. The hybrid discrete wavelet transform (DWT) and discrete cosine transform (DCT) based method improves the robust performance of the encrypted domain watermarking scheme. The watermark extraction can be performed on both the plaintext and the encrypted domains. We also give an estimation of the expanding factor after watermark embedding in the encrypted domain. At last, we discuss the watermark attacks that are available in the encrypted domain. Taking Haar wavelet transform for example, we conduct the experiments on the visual quality and the robustness of our watermarking scheme, which demonstrate that the entire performance is satisfactory.