An New Image Watermarking Scheme Based on Gerchberg-Saxton Algorithm and Integer Wavelet Transform 

This paper combines Gerchberg-Saxton (GS) algorithm with the integer wavelet transform (IWT) and proposes an image watermarking encryption scheme with better security, stability and imperceptibility. Firstly, the Fourier transform domain's modulus is replaced by the known amplitude information by the iterative principle of the GS algorithm. The noise-like initial image can be obtained when the similarity satisfies certain constraints. Then, variable step Joseph space scrambling and pixel value bit processing are used to enhance anti-interference ability. Finally, IWT decomposes the cover image into four subbands with different frequencies. After embedding all the information of the secret image into each sub-band bit by bit, the visually significant cypher image is obtained, highlighting the imperceptible characteristics. The carrier and the regular images' hash values are calculated using the SHA-256 function. The RSA mode is used to update the key as the initial value of the hyperchaotic system while enhancing the security of the key, producing the password stream encrypted and embedded. The innovation of this paper is the introduction of the GS algorithm, which converts the image amplitude information into phase information and encrypts it as the initial image. Simulation experiments and in-depth performance analysis confirm the proposed method's efficacy and security.