Block lightweight encryption scheme for securing internet of things data and information

Healthcare Internet of Things (HIoT) systems increasingly process multimedia data, yet existing Lightweight Cryptosystems (LWCs) often provide insufficient confusion, diffusion, and security due to their short key and block sizes. These limitations also expose them to key-related attacks and Cipher Block Chaining (CBC) eroding. To address these challenges, this work proposes a new multimedia-oriented LWC in which only a single block is encrypted or decrypted, significantly reducing computational overhead. Elliptic Curve Diffie–Hellman (ECDH) is employed for key establishment, and a dedicated Image_XOR module—combining secure pseudorandom number generation with XOR operations—is designed to enhance confusion, diffusion, and nonlinearity. The scheme applies SHA-256 to the concatenated bytes of the Shared Secret Key (SSK) and the plain image to generate a hash value (hashval). The plain image, SSK, and hashval are processed through the Image_XOR module to produce the encrypted image, while hashval is further encrypted using a Modified Caesar cipher (MCaesar). Decryption reverses the operations using the corresponding MCaesar_Dec module. Comprehensive evaluations—including sensitivity, statistical analyses, and noise-attack resistance—demonstrate that the proposed LWC exhibits strong robustness, high key and plaintext sensitivity, and superior performance relative to classical LWC designs. Its very low processing time and reduced memory footprint indicate suitability for real-time deployment on resource-constrained IoT devices. Overall, the findings confirm that the proposed LWC achieves strong security with minimal resource consumption, making it highly suitable for modern HIoT environments.