Multi-image encryption based on an extended chaotic map and a directional shift transformation

The proposed image encryption method is based on an extended logistic-based chaotic map integrated with a directional shift for enhanced randomness, security, and resistance to cryptographic attacks. Along with the control parameter, the new chaotic sequence, which utilizes two previous values, significantly enhances complexity and unpredictability. This modification, therefore, ensured higher sensitivity to initial conditions and resistance to differential, brute-force, and known plaintext attacks. The encryption scheme incorporated a directional shift transformation to further obscure pixel locations and enhance security. The key matrix decides the number and direction of shifts punctuated on each pixel. The transformation shifted pixels in one of four possible primary directions-lefthand, right-hand, upside-down, or downside. This created a highly unpredictable relocation mechanism, minimizing the correlation between the adjacent pixels in the encrypted images. Due to the implementation of a suitable algorithm for the key extracted from the input image, a slight change in the original image led to huge differences in encryption outputs, assuring statistical and cryptanalytic attacks. Security analyses carried out, including histogram analysis and correlation coefficient computation, have also confirmed the effectiveness of the scheme.