A Novel Two-dimensional SHIELD map for Audio Data Encryption with Two-step Confusion and Dynamic Diffusion Process

Digital audio communications involve sensitive information that requires secure transmission over unsecured networks. However, traditional encryption methods are costly for real-time applications due to the large size and high correlations in the audio data. Chaos-based encryption offers computational efficiency and resistance to cryptographic attacks. This research proposes a novel SHIELD map, combining sine, Logistic, and exponential functions with modular operations to enhance chaotic behaviour. A two-step confusion process using a novel bit-level operation and the Fisher-Yates algorithm, along with a dynamic diffusion mechanism based on the improved sine-tangent map, strengthens the proposed audio encryption algorithm. The encryption scheme is evaluated against various cryptanalysis methods, demonstrating a 2⁵¹² bit keyspace, 7.999 information entropy, 0.003 correlation coefficient, and NSCR and UACI values of approximately 99.60% and 33.50%, respectively. Additionally, the algorithm achieves high fidelity in decrypted audio with a signal-to-noise ratio exceeding 35 dB and perceptual evaluation of speech quality scores ranging from 4.0 to 4.5. The results confirm the proposed method’s robustness, efficiency, and suitability for secure real-time audio transmission.