Secured Asymmetric Image Cipher (SAIC) Algorithm for Efficient and High-Security Image Encryption

Abstract

Privacy in digital image transmission over public networks has become a critical concern. Traditional cipher methods often fail to provide robust protection against known-plain image attacks and lack sensitivity to changes in the source image. This study proposes an efficient Secured Asymmetric Image Cipher (SAIC) algorithm employing a variable-sized secret key. The technique generates two distinct keys via a key generation (KG) algorithm: one for encryption and another for decryption. The encryption process integrates mixing, key-dependent permutation and substitution to scramble images into an unintelligible format. The decryption process uses inverse operations to retrieve the original image. The proposed approach ensures high levels of security and efficiency, with performance measures including NPCR > 99.99%, UACI > 36.7% and DR > 97%. The method combines asymmetric key cryptography with advanced diffusion and confusion strategies, making it computationally secure, fast and suitable for practical deployment in image processing and communication systems.