Abstract

In recent years, numerous image encryption schemes have been developed that demonstrate
diferent levels of efectiveness in terms of robust security and real-time applications. While a few
of them outperform in terms of robust security, others perform well for real-time applications
where less processing time is required. Balancing these two aspects poses a challenge, aiming to
achieve efcient encryption without compromising security. To address this challenge, the proposed
research presents a robust data security approach for encrypting grayscale images, comprising fve
key phases. The frst and second phases of the proposed encryption framework are dedicated to
the generation of secret keys and the confusion stage, respectively. While the level-1, level-2, and
level-2 difusions are performed in phases 3, 4, and 5, respectively, The proposed approach begins
with secret key generation using chaotic maps for the initial pixel scrambling in the plaintext image,
followed by employing the Fibonacci Transformation (FT) for an additional layer of pixel shufing.
To enhance security, Tribonacci Transformation (TT) creates level-1 difusion in the permuted image.
Level-2 difusion is introduced to further strengthen the difusion within the plaintext image,
which is achieved by decomposing the difused image into eight-bit planes and implementing XOR
operations with corresponding bit planes that are extracted from the key image. After that, the
discrete wavelet transform (DWT) is employed to develop secondary keys. The DWT frequency subband (high-frequency sub-band) is substituted using the substitution box process. This creates further
difusion (level 3 difusion) to make it difcult for an attacker to recover the plaintext image from an
encrypted image. Several statistical tests, including mean square error analysis, histogram variance
analysis, entropy assessment, peak signal-to-noise ratio evaluation, correlation analysis, key space
evaluation, and key sensitivity analysis, demonstrate the efectiveness of the proposed work. The
proposed encryption framework achieves signifcant statistical values, with entropy, correlation,
energy, and histogram variance values standing at 7.999, 0.0001, 0.0156, and 6458, respectively.
These results contribute to its robustness against cyberattacks. Moreover, the processing time of
the proposed encryption framework is less than one second, which makes it more suitable for realworld applications. A detailed comparative analysis with the existing methods based on chaos,
DWT, Tribonacci transformation (TT), and Fibonacci transformation (FT) reveals that the proposed
encryption scheme outperforms the existing ones.