Extended Dual-Message QR Codes With Visual Secret Sharing

The camera serves as one of the primary sensors enabling smartphones to interact with the physical world, making it an essential tool for various interactive applications. By exploring the camera's unique way to recognize module bit values in the QR code decoding algorithm, this letter enhances dual-message QR codes by integrating visual secret sharing (VSS) functionalities. Each QR code encodes two distinct messages that can be read by standard QR code readers: one readable at close range and the other at a distance. In addition, the proposed (t, n) VSS scheme allows the confidential message to be revealed by stacking t or more of the n QR codes, while fewer than t QR codes disclose no information about the secret. Readability tests confirm that both messages in each QR code are accessible via standard smartphone QR code apps, and that the confidential message is recognizable to the human eye. Security analyses validate that the confidential message is reliably protected. Compared to previously reported multilayer QR codes, the proposed scheme encodes three layers of messages within a single QR code, archiving a higher information payload. Moreover, the capability to visually reveal the additional confidential message by stacking QR codes without requiring any computational processing is a notable advantage.