(2,2) Threshold Robust Visual Secret Sharing Scheme for QR Code Based on Pad Codewords

Quick response (QR) code has been used widely because of its advantages, such as, fast reading, error correction, and encoding multiple types of data. More and more researches on the combination of QR and visual cryptography have emerged, but there are few robust visual secret sharing scheme (VSS) for QR code. In this paper, we propose a robust (2, 2) threshold VSS for QR code based on pad codewords. We utilize the bug of no checking on the pad codewords when encoding the QR code, we encode initial shadows shared with secret image as pad codewords of cover QR code images to generate QR code shadows. In this way, the decoding results of shadow QR code images are identical with those of cover QR code images, no doubt arises when shadow images are exposed to the public channel. While a certain degree of damage and noise appearing in the shadow images, the secret can still be revealed, so the scheme is robust, which is important for practice. The experimental results demonstrate the effectiveness and robustness of our scheme.