Lightweight XOR-based visual cryptography using random shares for secure colour image sharing with minimal shares

Abstract In the current digital environment, safeguarding visual data from unauthorized use remains a substantial challenge. Sensitive imagery, including biometric, medical and defence images, represents a frequent target of destructive cyberattacks. Although conventional visual cryptography approaches achieve satisfactory results in rendering visual content unreadable, these schemes often present serious drawbacks that include excessive computation, pixel expansion and reduced reconstruction quality. This paper suggests a new method and concept of lightweight visual cryptography based on the use of bitwise operations (specifically XOR) for secured colour image sharing. This methodology employs three non-expansible shares while providing the user with lossless encryption and low computation in addition to strong statistical and differential attack resistance during encryption and decryption. The proposed method utilizes a cryptographically secure pseudo-random number generator (CSPRNG) and reversible XOR bitwise operations to determine and generate three unique unreadable shares. Tests and experiments reveal that the resulting shares have high reconstruction quality (PSNR > 40 dB), an ideal degree of randomness (entropy ≈ 7.997) and tolerable processing time (in comparison to traditional XOR-, polynomial- and CRT- based visual cryptography schemes). The new method and concept emphasize the merging of simplicity, scalability, and robustness in a computationally sound and secure solution for real-time use in areas such as military imaging, biometric authentication, and multi-media communication.