Enhancing Internet of Things communications: Development of a new S-box and multi-layer encryption framework

The growth of IoT applications has revolutionized sectors like security and home automation but raised concerns about data breaches due to device limitations. This research proposes a novel substitution box and cryptographic scheme designed to secure data transmission in IoT devices like smartphones and smartwatches. The proposed research has two phases: (I) generation of a substitution box (S-box) which is proposed by dividing phase space into 256 regions (0–255) using a random initial value and control parameter for the Piecewise Linear Chaotic Map (PWLCM), iterated multiple times, and (ii) a new encryption scheme, which is proposed by employing advanced cryptographic techniques such as bit-plane extraction, diffusion, and a three-stage scrambling process (multiround, multilayer, and recursive). Scrambled data is substituted using multiple S-boxes, followed by XOR operations with random image bit-planes to generate pre-ciphertext. Finally, quantum encryption operations, including Hadamard, CNOT, and phase gates, are applied to produce the fully encrypted image. The research evaluates the robustness of the proposed S-box and encryption scheme through experimental analyses, including nonlinearity, strict avalanche criterion (SAC), linear approximation probability (LAP), bit independence criterion (BIC), key space, entropy, correlation, energy, and histogram variance. The proposed approach demonstrates an impressive statistical performance with key metrics such as nonlinearity of 108.75, SAC of 0.5010, LAP of 0.0903, BIC of 110.65, a key space exceeding $2^{100}$, entropy of 7.9998, correlation of 0.0001, and energy of 0.0157. Furthermore, the proposed encryption scheme can encrypt a plaintext image of size 256 × 256 within one second which demonstrates its suitability for IoT devices that require fast computation.