The SMA: A Novel 2D Matrix-Based Lightweight Block Cipher for IoT Security

The rapid expansion of Internet of Things (IoT) and mobile devices has intensified the demand for lightweight cryptographic algorithms capable of delivering strong security with minimal computational overhead. This work presents the SMA, a Secure Matrix-Based lightweight block cipher designed to meet these requirements through a 64-bit block and 80-bit key Substitution–Permutation Network (SPN) optimized for constrained environments. The SMA combines a nibble-wise PRESENT S-box with a fully index-based 2D matrix permutation to provide high non-linearity and efficient full-bit diffusion, supported by an enhanced key schedule that increases round-key diversity and mitigates key-dependent weaknesses. The proposed method replaces the complex linear diffusion layers used in existing lightweight ciphers such as GIFT, RECTANGLE, and PRESENT with a low-cost two-dimensional permutation that improves practical performance. Experimental evaluation demonstrates that the SMA achieves 98.5% non-correlated outputs, an average 50% bit error rate under both plaintext and key variations, and a 100% pass rate across fifteen NIST SP 800-22 statistical tests in nine data categories. Software-based implementation further confirms the correctness and applicability of the SMA for IoT-oriented simulation environments. Moreover, no exploitable differential or linear trails were identified across the full 20-round design. These results indicate that the SMA provides strong confusion, diffusion, and statistical randomness while maintaining competitive performance for secure IoT and mobile encryption applications.