High-Payload QR Code Secret Hiding Mechanism Based on Hadamard Matrix

Code Division Multiple Access (CDMA) utilizes orthogonal matrices to transmit data without interference. Building upon this concept, this paper introduces a multi-layer secret message hiding mechanism for QR codes based on the Hardman matrix. By finely adjusting pixel values, the secret message can be embedded within the modules of the original QR code. Furthermore, a single module can accommodate multiple embedding processes, thereby enhancing the capacity for secret message insertion. The resulting marked QR code remains readable by any standard QR code decoder, preserving the public message. This meaningful marked QR code helps minimize the attention of malicious individuals. Experimental evaluations were conducted to assess the performance of the proposed scheme, and the results demonstrated significantly improved secret payload capacity compared to previous studies.