Comparative Analysis of Visual Cryptographic Techniques for Secure Image Encryption

Visual cryptography scheme (VCS) enables secure image sharing by splitting a visual secret into multiple shares, each of which reveals no information in isolation. This paper presents a comparative analysis of six distinct visual cryptographic techniques Pixel Expansion, CMYK Decomposition, XOR Encryption, Modular Arithmetic, Bit-Level Decomposition, and AES-based encryption applied to binary, grayscale, and colored images. Each method is implemented and evaluated based on key metrics, including Peak Signal-to-Noise Ratio (PSNR), Mean Normalized Cross-Correlation (MNCC), computational efficiency, and robustness against cryptographic attacks. Experimental results show that Pixel Expansion yields high security for binary images but incurs notable pixel distortion and image enlargement. Bit-Level Decomposition preserves structural detail in grayscale images, while XOR and Modular Arithmetic methods offer lightweight and fast encryption, albeit with strict shared dependency. CMYK Decomposition and AES-based approaches provide effective protection for colored images, with AES achieving the highest security at the cost of computational complexity. The analysis demonstrates trade-offs between visual fidelity, security, and performance, offering guidance on selecting suitable techniques for secure image transmission across diverse application domains.