A novel secure key generation and SPN-based transformation algorithm for greyscale image encryption

In today's digital age, securing sensitive visual data is crucial, particularly in fields like medical imaging and secure communication. This paper presents a novel greyscale image encryption algorithm that combines a secure message-based key generation approach with a substitution-permutation network (SPN) for enhanced security. The algorithm uses a user-specified parameter 'N' an input image, and a secret message to derive cryptographic parameters via a SHA-256 string for a Henon map. The map generates two arrays, x and y matching the image dimensions, which are used to create an XOR-based mask. Before applying the mask, the image undergoes P-rounds of SPN transformations, involving substitution and permutation operations. These operations employ a logistic map for randomness, ensuring robust encryption. Decryption reverses these steps. The paper highlights the algorithm's computational efficiency and strong security features, making it suitable for diverse applications.