Cited by 14Chaos-based Image/Signal EncryptionComputer Science and EngineeringAdvanced Steganography and Watermarking Techniques

A novel color image encryption algorithm based on fractional-order conservative memristive hyperchaotic system and extended zig-zag transform

Open access
Meng, Fanqi, Wu, Gang, Zhang, Juxiao·2025·Journal of King Saud University Computer and Information Sciences

Abstract

Color images are a valuable information carrier. This paper presents a novel image encryption scheme based on fractional-order conservative memristive hyperchaotic system (FCMHS) and extended Zig-Zag transform to protect images from being attacked. First, the dynamic characteristics of FCMHS were systematically studied and analyzed, and its potential application value in the field of information security is verified. The pseudo-random sequences generated by FCMHS passed all the tests of the National Institute of Standards and Technology (NIST). Second, a new extended Zig-Zag confusing method is designed, which realizes the scrambling of pixels in different channels of a color image. Finally, the performance of the designed encryption algorithm is analyzed using key space, information entropy, histogram, differential attack, correlation coefficient and robustness analysis. The average number of pixels change rate (NPCR) and uniform average change intensity (UACI) values of the encryption scheme are 99.61% and 33.46%, respectively. Additionally, the encryption time is only 0.12533 s for a color image of size $$256\times 256$$ . The experimental results demonstrate that our algorithm has better encryption performance and security.

AI snapshot

Written from the paper’s full text.

TL;DR

The paper proposes a color image encryption scheme combining a fractional-order conservative memristive hyperchaotic system (FCMHS) with an extended 3D Zig-Zag transform. It reports strong security metrics, including average NPCR 99.61%, UACI 33.46%, and 0.12533 s encryption time for a 256×256 color image.

Key findings

  • The FCMHS-generated pseudo-random sequences passed all 15 NIST-800-22 subtests, with average p-values within [0.01, 1].
  • The encryption scheme achieved average NPCR and UACI values of 99.61% and 33.46%, respectively, close to theoretical ideals (99.6094% and 33.4635%).
  • Key space is reported as 10^(9×15) ≈ 2^448, exceeding the 2^100 threshold; key sensitivity tests with 10^-15 perturbations produced pixel change rates above 99.6%.
  • Encrypted images had information entropy close to 8 (e.g., Lena R/G/B: 7.9976, 7.9977, 7.9971) and near-zero correlation coefficients, while encryption time was 0.12533 s for 256×256 and 0.53289 s for 512×512.

Methods

  • Design: A fractional-order conservative memristive hyperchaotic system is built from a 4D conservative chaotic system and a fractional-order multistable memristor; an extended Zig-Zag transform extends 2D Zig-Zag scrambling to 3D RGB channel rearrangement.
  • Encryption: Color images are divided into blocks, scrambled via chaotic-sequence-selected Zig-Zag transforms, permuted, diffused using a Fibonacci Q-matrix, and row/column substituted; decryption reverses these steps.
  • Data and analysis: Tests used Lena (256×256), Baboon (512×512), and Airplane (512×512) from the USC-SIPI database; analyses included phase/bifurcation/Lyapunov/Kaplan-Yorke diagrams, NIST tests, key space, key sensitivity, histogram variance, correlation, NPCR/UACI, information entropy, cropping, noise, and execution time.

Limitations

  • The paper does not state an explicit limitations section; it only lists future research directions such as combining multiple fractional-order chaotic systems and exploring quantum computing for large images.
  • Evident from the text: the execution-time comparison in Table 9 uses different computer specifications across schemes, so the reported speed advantage is not hardware-controlled.
  • Evident from the text: security validation is empirical (statistical and robustness tests) and does not include formal cryptanalytic proofs or side-channel/chosen-ciphertext attack analysis.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1007/s44443-025-00163-7

Cites

49 of 49 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 8 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    The chaotic sequence generated by the proposed system passed all the test items of NIST-800-22.

    “It can be seen from the test results in Table 1 that the chaotic sequence passed all the test items.”
    Quote in the paperSubstantial claim
  • Findingown data

    The FCMHS exhibits strongly nonperiodic orbits in the spaces x∼y, x∼z, y∼z, x∼w, x∼w∼u and x∼y∼z.

    “spaces x ∼ y , x ∼ z , y ∼ z , x ∼ w , x ∼ w ∼ u and x ∼ y ∼ z .”
    Quote in the paperSubstantial claim
  • Findingown data

    The Lyapunov exponent is widely positive in the initial value definition domain of FCMHS.

    “the Lyapunov exponent is widely positive in the initial value definition domain of FCMHS”
    Quote in the paperSubstantial claim
  • Findingown data

    The Kaplan-Yorke fractal dimension values of the FCMHS are always greater than 4.

    “the values of the Kaplan-Yorke fractal dimension are always greater than 4”
    Quote in the paperSubstantial claim
  • Findingown data

    The FCMHS has complex dynamic behavior changes within the parameter interval.

    “The bifurcation diagram shows that the system has complex dynamic behavior changes within the parameter interval”
    Quote in the paperSubstantial claim
  • May combine two claims. 16
  • The quote only partly states this claim. 2
  • Classified as probably not a substantial claim. 4
  • May combine two claims.

    Findingown data

    The histogram of the original images does not demonstrate a uniform distribution, whereas the histogram of the encrypted images displays a uniform distribution.

    “As can be seen in Fig. 12 (a-c), the histogram of the original images do not demonstrate a uniform distribution.Conversely, in Fig. 12 (d-f) the histogram of the encrypted images display a uniform distribution.”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Findingown data

    The average NPCR and UACI values of the encryption scheme are 99.61% and 33.46%, respectively.

    “The average number of pixels change rate (NPCR) and uniform average change intensity (UACI) values of the encryption scheme are 99.61% and 33.46%, respectively.”
    Quote in the paperSubstantial claim
  • The quote only partly states this claim.

    Findingown data

    For encrypted Lena, Baboon, and Airplane images, correlation coefficients between neighboring pixels in horizontal, vertical, and diagonal directions are close to 0.

    “The presence of image pixel points closed to 1 in three directions before encryption and close to 0 in the encrypted image indicates that the proposed encryption algorithm can effectively break the correlation between pixels.”
    Quote in the paperSubstantial claim
  • The quote only partly states this claim.

    Findingown data

    The proposed scheme has a very large key space compared with recent literature.

    “It is clear that the proposed scheme has a very large key space.”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Findingown data

    For Lena ciphertext cropped at rates 1/16, 1/8, and 1/4, the decrypted images are somewhat blurred but the image content can still be roughly seen.

    “The resulting figure shows that the decrypted image is somewhat blurred and the image content can still be roughly seen”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Findingcitation

    Assuming a system accuracy of 10^-15, the total key space of the proposed scheme is 10^9×15 ≈ 2^448, which far exceeds the minimal threshold of 2^100.

    “Assuming a system accuracy of 10 -15 , the total key space is 10 9×15 ≈ 2 448 , which far exceeds the minimal thresh- old outlined in 2 100 (Koçak et al. 2024).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Koçak et al. 2024

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Findingown data

    The encrypted image bears no correlation with the original image, while the reconstructed image is visually indistinguishable from the original.

    “Figure 9 illustrates that the encrypted image bears no correlation with the original, while the reconstructed image is visually indistinguishable from the original.”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Interpretationreasoning

    The extended Zig-Zag transform enhances the complexity of the disarrangement algorithm and is more capable of combating statistical attacks than the traditional Zig-Zag transform method.

    “which enhances the complexity of the disarrangement algorithm, and the Extended Zig-Zag transform is more capable of combating statistical attacks than the traditional Zig-Zag transform method.”
    Quote in the paperSubstantial claim
  • Classified as probably not a substantial claim.

    Premisecitation

    Chaotic systems have high sensitivity and unpredictability to initial conditions and system parameters.

    “Chaotic systems have properties such as high sensitivity and unpredictability to initial conditions and system parameters (Youssef et al. 2024).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Youssef et al. 2024 source
  • Classified as probably not a substantial claim.

    Premisecitation

    Cang et al. (2017) presented a Hamiltonian energy-conserving 4D conservative chaotic system with complex dynamical properties.

    “Cang et al. (2017) presented a Hamiltonian energy-conserving 4D conservative chaotic system with complex dynamical properties.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Cang et al. (2017) source
  • May combine two claims.

    Interpretationown data

    The widely positive Lyapunov exponent of FCMHS is conducive to achieving strong diffusivity and high obfuscation of the global pixels of an image, and thus effectively resisting statistical attacks and differential attacks.

    “which is conducive to achieving strong diffusivity and high obfuscation of the global pixels of the image, and thus effectively resisting statistical attacks and differential attacks.”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Premisecitation

    Unlike dissipative chaotic systems, conservative chaotic systems usually do not have an attractor structure but exhibit stronger pseudo-random characteristics.

    “Unlike DCSs, CCSs usually do not have the attractor structure (Ji'e et al. 2022) but exhibit stronger pseudo-random characteristics.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Ji'e et al. 2022

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Classified as probably not a substantial claim.

    Premisecitation

    Image encryption technology can effectively prevent sensitive images from being stolen or tampered with during transmission and storage.

    “Image encryption technology can effectively prevent sensitive images from being stolen or tampered with during transmission and storage (Kaur et al. 2022).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Kaur et al. 2022 source
  • May combine two claims.

    Interpretationreasoning

    The extended Zig-Zag transform method achieves effective pixel rearrangement in both spatial and channel dimensions, which significantly enhances the disambiguation degree and encryption strength of the image and shows a good comprehensive performance.

    “The method achieves effective pixel rearrangement in both spatial and channel dimensions, which significantly enhances the disambiguation degree and encryption strength of the image and shows a good comprehensive performance.”
    Quote in the paperNot a substantial claim
  • May combine two claims.

    Interpretationown data

    The proposed encryption scheme is effective and yields satisfactory performance.

    “These results confirm that the proposed encryption scheme is effective and yields satisfactory performance.”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Interpretationown data

    The proposed algorithm has better encryption performance and security.

    “The experimental results demonstrate that our algorithm has better encryption performance and security.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Combining Zig-Zag transform with a chaotic system enhances the complexity and security of image encryption and improves resistance to statistical and analytical attacks.
    • Rests on an assumption: The security of image encryption methods using only chaotic systems depends on the complexity of chaotic systems and should be explored in combination with other theories to improve security.
  • May combine two claims.

    Interpretationown data

    The encryption algorithm based on FCMHS and extended Zig-Zag transform can resist differential and selective plaintext attacks.

    “indicating that the encryption algorithm based on FCMHS and extended Zig-Zag transform has good sensitivity to plaintext and can resist differential and selective plaintext attacks.”
    • Also stated in: § 6 Conclusion · plain
      “It is able to resist statistical statistics, differential attacks, cropping attacks and Noise attacks.”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Interpretationown data

    The proposed encryption algorithm has very good robustness and can resist noise attacks.

    “indicating that the encryption algorithm designed in this paper has a very good robustness able to resist noise attacks.”
    • Also stated in: § 6 Conclusion · plain
      “It is able to resist statistical statistics, differential attacks, cropping attacks and Noise attacks.”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Interpretationown data

    The proposed algorithm avoids the effect of data loss to a certain extent and recovers the original image to a large extent.

    “demonstrating that the algorithm avoids the effect of data loss to a certain extent and recovers the original image to a large extent.”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Interpretationreasoning

    The key generation mechanism has good randomness and a highly complex state space, which effectively avoids key guessing and exhaustive attacks.

    “Therefore, the key generation mechanism has good randomness and highly complex state space, which effectively avoids key guessing and exhaustive attacks.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The security of image encryption methods using only chaotic systems depends on the complexity of chaotic systems and should be explored in combination with other theories to improve security.
  • May combine two claims.

    Interpretationown data

    The proposed image encryption algorithm has good key sensitivity and security.

    “which reflects the system's good key sensitivity, and significantly enhances the resistance to similar key attack and exhaustive attack.”
    • Also stated in: § 5.2 Key sensitivity analysis · hedged
      “which indicates that the proposed image encryption algorithm has good key sensitivity and security.”
    Quote in the paperSubstantial claim
  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationnone given

    The extended Zig-Zag transform method proposed in this paper makes full use of the information redundancy and correlation between dimensions.

    “The extended Zig-Zag transform method proposed in this paper makes full use of the information redundancy and correlation between dimensions.”
    Quote in the paperNot a substantial claim
22 of 22
  • The paper relies on this without support.

    The nonlinear characteristics of memristors can cause a system to exhibit more complex chaotic properties.

    “The nonlinear characteristics of memristors can cause the system to exhibit more complex chaotic properties.”
  • The paper relies on this without support.

    The introduction of a memristor makes a chaotic system more sensitive to initial conditions, which can improve the security performance of an image encryption algorithm based on that system.

    “Moreover, the introduction of the memristor makes the system more sensitive to the initial conditions, which can improve the security performance of the image encryption algorithm based on the memristor chaotic system.”
  • The paper relies on this without support.

    Conservative chaotic systems have not been widely studied.

    “In contrast, conservative chaotic systems (CCSs) have not been widely studied.”
  • The paper relies on this without support.

    Image data has a larger volume and stronger inter-pixel correlation than traditional text data, so image encryption requires higher efficiency and stronger security.

    “Compared with traditional text encryption, image data has a larger volume and stronger inter-pixel correlation, which determines that its encryption processing requires higher efficiency and stronger security in design.”
  • The paper relies on this without support.

    Combining Zig-Zag transform with a chaotic system enhances the complexity and security of image encryption and improves resistance to statistical and analytical attacks.

    “The combination of this transform with a chaotic system enhances the complexity and security of image encryption and improves the resistance to statistical and analytical attacks.”
  • The paper relies on this without support.

    The security of image encryption methods using only chaotic systems depends on the complexity of chaotic systems and should be explored in combination with other theories to improve security.

    “The security of image encryption methods using only chaotic systems depends on the complexity of chaotic systems and should be explored in combination with other theories to improve the security of image encryption.”
  • The paper relies on this without support.

    The properties of memristor have more advantages in constructing conservative chaotic system.

    “The properties of memristor have more advantages in constructing conservative chaotic system.”
7 of 7

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Noise densities disagree with Fig. 15 caption

    Minor

    The text says the three salt-and-pepper noise densities are 0.01, 0.05, and 0.1, but the figure caption labels them 0.01, 0.1, and 0.2.

  • Pixel vector loses the color-image dimension

    Minor

    The input contains 3MN values, but Step 6 creates a permutation of only MN positions and Step 8 specifies an M × N matrix. The stated steps do not account for the other two color channels while claiming to encrypt and decrypt a color image.

2 of 2

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Authors
Meng, F., Wu, G., & Zhang, J.
Affiliations
  • Yancheng Teachers University (CN)
  • Nanjing Normal University of Special Education (CN)
Corresponding author
  • Meng, Fanqi
  • Zhang, Juxiao
Venue
Journal of King Saud University Computer and Information Sciences
Published
2025-08
Volume
37
Issue
6
ISSN
  • 1319-1578 (ISSN-L)
  • 2213-1248
OpenAlex
W4412992206
Cited by
14
References
43
Citations by year
2026: 13 · 2025: 1
FWCI
5.25
Type
journal article
Language
en
Open access
Locations
  • Journal of King Saud University - Computer and Information Sciences (publishedVersion, cc-by-nc-nd)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
Natural Science Research of Jiangsu Higher Education Institutions of China (23KJA120004)
Topics
  • Physical Sciences › Computer Science › Computer Vision and Pattern Recognition › Chaos-based Image/Signal Encryption
  • Physical Sciences › Computer Science › Artificial Intelligence › Computer Science and Engineering
  • Physical Sciences › Computer Science › Computer Vision and Pattern Recognition › Advanced Steganography and Watermarking Techniques
Keywords
color image encryption, conservative chaotic systems, pixel scrambling, pseudorandom sequence generation, key space analysis, NPCR and UACI, differential attack resistance, image scrambling

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