Mutual Authentication via Non-Monotonic XOR Visual Cryptography

We propose a novel mutual authentication protocol based on an enhanced XOR-based visual cryptography scheme exhibiting a non-monotonic access structure. A secret image is split into four visual shares such that the XOR of exactly three shares reveals a clear and human-readable image, while the XOR of one, two, or all four shares produces a visually blurred result. This property is achieved through carefully designed visual cryptography basis matrices. Using this construction, we design a lightweight challenge–response mutual authentication protocol requiring minimal cryptographic operations and relying primarily on XOR operations and human visual verification while assuming a trusted authority for initial share distribution. Security analysis shows that the protocol provides resistance against impersonation and eavesdropping attacks, while replay protection can be achieved by incorporating standard session management techniques. Experimental validation confirms the effectiveness of the proposed scheme, making it suitable for human-centric and resource-constrained environments.