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Visual cryptography is a technique that allows visual information to be encrypted in such a way that the decrypted information appears as a visual image. To enhance visual cryptography for color images, the proposed technique utilizes the RGB color space. The process involves several steps, including color decomposition and error diffusion. Color decomposition breaks down the color image into its constituent color channels (red, green, and blue). Each color channel is then treated as a separate grayscale image and undergoes visual cryptography individually. Error diffusion is a technique used in half-toning, where the quantization residual (the difference between the original pixel value and the quantized value) is distributed to neighboring pixels that have not been processed yet. This helps in maintaining the overall visual quality of the decrypted image. In the proposed technique, the image is encrypted using four shares: cyan, magenta, yellow, and a mask. The mask is generated using a random function and consists of half-black and half-white pixels in each block. To review the secret image, all the shares are stacked together. By combining the shares, the original image can be visually decrypted. The addition of the AES algorithm can further enhance the security of the encryption process. Advanced Encryption Standard (AES) is a widely used symmetric encryption algorithm that provides strong cryptographic protection. By incorporating the AES algorithm at an appropriate stage in the visual cryptography process, the security of the encrypted shares can be strengthened. The specific details of where and how the AES algorithm is incorporated would depend on the implementation and design choices of the visual cryptography system.
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