A Kind of Verifiable Visual Cryptography Scheme

The visual cryptography scheme (abbreviated VCS) proposed by Naor and Shamir provides a way to encrypt a secret black-white image into shares. A qualified group of participants can recover the secret message without using any cryptographic computation. But the original scheme can easily be corrupted by malicious participant. We propose an extension of VCS to verify cheaters based on digital watermarking. Without any additional information and cryptographic computation, every participant can verify the validity of shares of other participants only by watermark extraction operation. Thus the security of VCS is enhanced.