Cryptanalysis and design of chaos based image encryption schemes

Wong , Kuan Wai (2025) Cryptanalysis and design of chaos based image encryption schemes. PhD thesis, UTAR.

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Abstract

Chaos theory has been widely applied in designing image encryptionschemes due to its deep connection with cryptographic properties, such assensitivity to initial conditions and unpredictability. However, many existing image encryption schemes have been shown to be insecure against cryptanalysis. Cryptanalysis is essential for uncovering potential vulnerabilities, as it evaluates the security of encryption schemes, identifies weaknesses, and guides the development of more secure frameworks. Our research reveals that the scheme proposed by Biswas et al. is vulnerable to known plaintext attacks, requiring a time complexity of 2264.28 encryptions. This is 2183.72 times faster than brute-force attacks. Similarly, a chosen plaintext attack on Ping et al.’s scheme reveals a reduced key space of 2216.51, down from the claimed 2356, and identifies inefficiencies in its Henon map-based sequential encryption method. These findings emphasize the need for a more comprehensive analysis of encryption schemes that utilize genetic algorithm and sequential encryption techniques. To address these challenges, we propose secure image encryption schemes that are based on enhanced chaotic maps. Specifically, we enhance the chaotic behavior of one-dimensional and two-dimensional chaotic maps using cascading techniques. This results in the development of the Logistic-Beta map, the 2D-Henonlog map, and the 2D-Sine-Henon Chaotic Map (2D-SHCM). Furthermore, we present a grayscale image encryption scheme utilizing a permutation-diffusion architecture, as well as a color image encryption scheme based on a genetic algorithm and the 2D-SHCM. Both schemes are designed to ensure high levels of confusion and diffusion in the encrypted images. Experimental results demonstrate that the proposed schemes effectively resist both statistical and differential attacks. These results highlight the importance of cryptanalysis of existing schemes to identify weaknesses and develop secure encryption methods. The proposed work underscores the need for robust chaotic maps, strong confusion and diffusion mechanisms, and thorough security evaluations as fundamental principles for designing reliable image encryption schemes.

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