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Fig. 2. Block diagram of the presented methodology, adapted is employed to fill the speech signal’s silence period, resulting
from [12]. in the audio ciphertext. The primary audio signal, compres-
sion and de-noising, and audio image conversion procedure
The investigation for more safe and efficient ways to pre- are the three basic components of the encryption technique.
serve speech confidentiality began after it became evident In a memristor chaotic system, the overlapping diffusion en-
from our study of traditional encryption methods that these cryption process and interactive channel shuffle are used to
techniques were ineffective for encrypting speech due to their generate the mask and cipher blocks. Fig. 3. depicts the
small key space, high sampling frequency, and complicated algorithm encryption process design.
switching process, which needed a larger processing unit and
more computation time. In 2023, ShiMing Fu et al [19], examined a novel four-
dimensional hyperchaotic system showed its fundamental
B. New Chaotic Methods: dynamic behavior, such as its bifurcation diagram, equilib-
Over the past 40 years, the scientific, mathematical, and engi- rium point stability, chaotic attractor, and Lyapunov expo-
neering communities have conducted a great deal of research nent spectrum. To stabilize the hyperchaotic system until it
on chaos, a very fascinating and complex nonlinear phenom- reaches equilibrium, a linear feedback control technique was
ena. Consequently, creating chaos has emerged as a prominent presented. The efficacy of this technique was demonstrated
field of study.chaotic systems are of high importance in engi- using both Multisim circuit simulation and embedded hard-
neering [14–16], and medical [17], applications.In this section, ware STM32 implementation. In addition, this paper applies
a general method of chaotic encryption will be provided as the designed hyperchaotic system to audio encryption. The
follows: cross-XOR operation method, which has a certain degree of
complexity and is easy to implement, is used by the audio
1) Continuous Time Chaotic Systems: encryption algorithm. The results of the experiment demon-
In 2021, Wanying Dai et al [18], proposed an audio encryption strate that, in the time domain, the encrypted audio sequence
algorithm based on Chen memristor chaotic system. The core is exactly the same as the original sequence; however, in
idea of the algorithm is to encrypt the audio signal into the the frequency domain, it appears as random noise, making
color image information. Most of the traditional audio encryp- it impossible to decipher the actual information carried by
tion algorithms are transmitted in the form of noise, which the audio. This demonstrates the efficacy of the hyperchaotic
makes it easy to attract the attention of attackers. To achieve key sequence-based cross-XOR operation method for audio
greater security, the authors employed a unique encryption encryption.
technique. First, the signal is compressed and denoised using
the Fast Walsh-Hadamard Transform (FWHT). The Discrete An innovative 4D hyperchaotic system given by system (1)
Cosine Transform (DCT) and the Fast Fourier Transform [19],:
(FFT) lack the good energy compression characteristics of the
FWHT. Additionally, the rectangular basis function of the Fast dx = a(y - x) + w (1)
Fourier Transform (FWHT) can be implemented in the digital dt
circuit more effectively than the triangular basis function, al- dy = cy - 10xz
lowing it to transform the reconstructed dual-channel audio dt
signal into the R and B layers of the digital image matrix, re- dz = -bz + 10xy
spectively. Moreover, the limited chaos range and nonuniform dt
distribution of the periodic window problems are resolved dw = dy + x2
by a novel Chen memristor chaotic system. Ultimately, the dt
overlapping diffusion encryption of the cryptographic block
the state variables in this case are x,y,z and w and the deriva-
tives of these variables are, in turn, dx/dt,dy/dt ,dz/dt and
dw/dt.
In 2020, Ehab Abdul Razzaq Hussein et al. [20], Based on the
double chaotic masking technique, an active secure commu-
nication system was applied to the information signal. From
this study, the following conclusions can be made:
