Quantum dot steganographic system based on multifarious fluorescence

Information security is crucial in today's era of big data, particulary in applications involving property, privacy, and military operations. While cryptography secures data content, steganography conceals its existence. Recently, optical steganography has gained attention for hiding data within optical elements. This method offers enhanced security, as the hidden text cannot be retrieved directly like a digital file but requires specific light-field environments or spectrometers for recovery. However, the concepts of cryptography and steganography are often confused in optical systems, and existing optical steganography methods rarely achieve large capacity, robustness, and security simultaneously. In this paper, we establish a clear boundary for cryptographic and steganographic optical systems based on the different functions performed by optical components. We then construct a quantum-dot film array-based steganographic system that simultaneously achieves high capacity, robustness, and security. The system is founded on a nonlinear mathematical model of quantum-dot fluorescence superposition and a spatial-spectral-temporal triple key to strengthen security. We perform theoretical analysis, simulations, and experiments to demonstrate its superior behavior. Finally, we propose a system solution for practical steganographic applications that can adapt to different security and capacity requirements. Moreover, the advancement of thin film technology in the future will represent a new step forward in the performance of the system.