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results. Thus, the combination of these three encryption meth-
ods (zigzag scan, RSA and chaos) makes the proposed TIC
cryptosystem quite strong and robust.
G. Comparison of Cryptosystem Performance with Related
Methods
TIC performance is compared with many related existing
image cryptosystems in order to evince its superiority. The
sample images of size 256 × 256 are used in this comparison
and the outcomes are illustrated in Tables VIII-X. Table VIII
shows the security comparison in terms of information en-
tropy, PSNR, UACI, NPCR, and correlation values along the
three directions. Table IX gives the key space comparison,
and Table X lists the speed analysis comparison with other
approaches.
For Table VIII, it can found that the presented scheme
achieves higher entropy scores or equal to those outcomes
acquired via other approaches except for Ref. [44] at Lena
image, Ref. [34] at Baboon and Peppers image, and Ref. [36]
at Baboon, Boat and Peppers images. Also, the PSNR val-
ues generated by the introduced algorithm are smaller than
the other current methods. Besides, this technique attains
better values in terms of NPCR except for Ref. [34] at Cam-
eraman image. Moreover, the UACI results produced by this
cryptosystem are larger or closer to those gained by other
algorithms expect for Ref. [44] at Lena image. Finally, the
correlation coefficients scores obtained via this mechanism
along three directions are lower or nearer in comparison with
the existing references.
Table IX reveals that the key space size of the proposed
technology is the largest as compared with other methods.
This is because using high dimensional Duffing and Lu¨ chaotic
systems with multiple initial conditions/control parameters.
Furthermore, the described mechanism possesses the shortest
ciphering time among the compared references as clarified in
Table X except for Ref. [16] at Cameraman, Lena, Barbara
and Peppers images of size (512 × 512), and Ref. [26] at Boat
image of size (256×256). It can be deduced from Tables VIII-
X that the TIC possesses a superior security performance and
high speed. Therefore, it is suitable for satisfying real-time
communication applications.
V. CONCLUSION
This article presents a new efficient image encryption strategy The authors have no conflict of relevant interest to this article.
based on combining zigzag scan, RSA coding and chaotic
systems. After splitting the input image into a specific number
of non-overlapping blocks, the zigzag scan is modified to
be with a variable starting pixel, then it is implemented in
two different directions in order to shuffle the image pixels.
Yousif, Hameed & Al-Zuhairi
Asymmetric key RSA algorithm is applied secondly on the
scrambled image. Finally, chaotic systems are utilized to
implement the confusion-diffusion processes. The important
conclusions about the proposed work can be summarized as
follows:
• Appling the zigzag scan in two different directions and
with a variable starting pixel on the non-overlapping
blocks yields a higher secure scrambling degree.
• Appling the RSA technique increases the security level
of the TIC by selecting a large prime number modulo
which requires an extremely long time to break it.
• Adopting higher dimensional chaotic maps improves
the resistance against the exhaustive attack since the
size of key space depends on the values of system pa-
rameters/initial conditions.
• The proposed TIC is very sensitive to the key alteration
such that the differences between the original and deci-
phered images are more than 99 % for a tiny change in
one of the TIC keys values.
• The presented cryptosystem is evaluated based on com-
prehensive performance analysis and comparison anal-
ysis with several common existing methods; the results
prove the encryption effectiveness of the TIC for all the
tested images.
• In summary, the TIC possesses a high sensibility to
the key change, a large key space, a high immunity
to the cryptographic attacks, and fast processing time.
Therefore, the presented approach provides a perfect
candidate for secure image applications such as online
wireless communication.
• For future work, the proposed technique can be applied
upon other types of digital images like color images,
medical images, biometric images or remote sensing
images. Also, the decryption time of the suggested
cryptosystem is slightly longer than the encryption time;
this time can be improved to make it more adequate for
real-time cryptographic applications.
CONFLICT OF INTEREST
REFERENCES
[1] A. S. Hameed, “Speech scrambling based on synchro-
nization of jointed dynamic parameter chaotic map,”
Telecommunications and Radio Engineering, vol. 80,
no. 8, 2021.