A deep quantization formalism for physically-induced key generation and secure image encryption

In this proposal, a physics-driven methodology for secure key generation and image encryption is proposed by employing the underlying stochastic nature of optical wave propagation through atmospheric turbulence. An optical wave propagating through this medium suffers random phase and amplitude distortions, leading to intermittent intensity fluctuations at the receiver end. This phenomenon serves as a high-entropy source of randomness that has been exploited in the proposed method. Building on this principle, a realistic optical propagation pipeline is developed by integrating turbulence-induced fluctuations, multiplicative distortion emanating from coherent interference, and additive noise. This results in a stochastic optical observation, and is further transformed into cryptographic binary sequences using a nonlinear deep quantization module. The robustness and statistical independence of the key generation mechanism is further enhanced by processing the quantized outputs using dithered thresholding, repetition-based error reconciliation, and cryptographic privacy amplification, resulting in a 256-bit secret key. The generated bit stream is employed in a hybrid image encryption framework that utilizes Arnold transform-based permutation and a zero-propagation 2D stream-diffusion engine. This combination ensures good confusion and diffusion properties while localizing transmission errors during decryption. The generated key stream has been statistically validated using the NIST SP 800-22 test suite, the results confirms the presence of randomness. The encryption scheme achieves good entropy, negligible pixel correlation, and resistance to differential attacks, as demonstrated by NPCR and UACI values.