Hybrid Image Encryption Scheme Using SPECK Block Cipher and Salsa20-Based DNA-Enhanced Key Generation

This paper presents a new hybrid image encryption algorithm, which combines the SPECK block cipher with a Salsa20-based key generation process. Although these factors have been integrated in the past, what is unique about our work is that DNA encoding and transformation are applied only to the key stream, not to the image data itself. The method produces a non-linear, irreversible key obfuscation layer that enhances the system’s resistance to key-based attacks at a relatively small cost to the overall computation of the main image encryption operation. The system will have the key generated by Salsa20 to 128 bits, converted by DNA complement and reverse operations, and finally loaded into the SPECK cipher to be encrypted. The approach provides a high-security level but with memory-efficient computation, and, therefore, it is resource-constrained and can be applied to IoT devices. The system shows robust results in NPCR (>99.6%), UACI (~33%), and entropy (7.99).