A Secured Data Transmission Model for Protecting IoT Gateway-to-Public Cloud Communication Using Enhanced Symmetric Encryption

Objectives: To develop a lightweight symmetric encryption model for securing IoT gateway-to-public cloud communication while improving confidentiality and execution efficiency. Method: The Enhanced Symmetric Cryptography Technique (ESCT) uses an eight-round block cipher with dual subkey mixing, popcount-based adaptive rotations, row-shuffling permutation, and final permutation. The method was evaluated on IoT sensor payloads using DES and Blowfish as baseline controls for encryption time, decryption time, and relative security strength. Findings: Experimental results show that ESCT achieved better computational efficiency than DES and Blowfish for IoT-cloud data transmission. At 100 KB, ESCT completed encryption in 31 ms compared with 52 ms for DES and 41 ms for Blowfish, and decryption in 29 ms compared with 49 ms and 38 ms, respectively. For the 1 MB payload test, ESCT required 302 ms, while DES and Blowfish required 492 ms and 429 ms. The comparative security evaluation also recorded a higher security strength score for ESCT (94%) than DES (78%) and Blowfish (84%). These findings confirm that the proposed dual-subkey, adaptive-rotation, and multi-permutation design improves ciphertext robustness while reducing execution cost in gateway-level IoT-cloud communication. Novelty: ESCT combines dual per-round subkeys, popcount-driven adaptive rotations, and layered permutations to harden IoT-cloud payloads without heavyweight hybrid-encryption overhead. Keywords: IoT Security, Cloud Communication, Symmetric Encryption, Lightweight Cryptography, ESCT