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<article xmlns:xlink="http://www.w3.org/1999/xlink">
  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Hybrid RNN-CNN-based model for PRNG identification⋆</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Dmytro Proskurin</string-name>
          <email>d.proskurin@gmail.com</email>
          <xref ref-type="aff" rid="aff1">1</xref>
          <xref ref-type="aff" rid="aff3">3</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Tetiana Okhrimenko</string-name>
          <xref ref-type="aff" rid="aff1">1</xref>
          <xref ref-type="aff" rid="aff3">3</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Sergiy Gnatyuk</string-name>
          <email>s.gnatyuk@nau.edu.ua</email>
          <xref ref-type="aff" rid="aff1">1</xref>
          <xref ref-type="aff" rid="aff3">3</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Dauriya Zhaksigulova</string-name>
          <email>dauriya.dzh@gmail.com</email>
          <xref ref-type="aff" rid="aff1">1</xref>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Nataliia Korshun</string-name>
          <email>n.korshun@kubg.edu.ua</email>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Borys Grinchenko Kyiv Metropolitan University</institution>
          ,
          <addr-line>18/2 Bulvarno-Kudriavska str., 04053 Kyiv</addr-line>
          ,
          <country country="UA">Ukraine</country>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>CQPC-2024: Classic</institution>
          ,
          <addr-line>Quantum, and Post-Quantum Cryptography</addr-line>
        </aff>
        <aff id="aff2">
          <label>2</label>
          <institution>D. Serikbayev East Kazakhstan Technical University</institution>
          ,
          <addr-line>19 D. Serikbayev str., 070004 Ust-Kamenogorsk</addr-line>
          ,
          <country country="KZ">Kazakhstan</country>
        </aff>
        <aff id="aff3">
          <label>3</label>
          <institution>National Aviation University</institution>
          ,
          <addr-line>1 Liubomyra Huzara ave., 03058 Kyiv</addr-line>
          ,
          <country country="UA">Ukraine</country>
        </aff>
      </contrib-group>
      <fpage>47</fpage>
      <lpage>53</lpage>
      <abstract>
        <p>Pseudorandom Number Generators (PRNG) are used in the financial sphere, medicine, game industry, networks and communication, statistical simulation, IT, security, authentication, and cryptography (key management, initialization vectors, one-time passwords). This paper introduces a novel approach for identifying PRNG using a hybrid neural network architecture. The proposed model integrates Recurrent Neural Networks (RNN) and Convolutional Neural Networks (CNN) to enhance the accuracy of classification. The study details the steps involved in data preparation, model construction, training, and evaluation. Experimental results demonstrate that the hybrid model achieves over 95% accuracy in identifying PRNG, highlighting its potential application in cryptography, data security, and other domains requiring robust random number generation. The model's high reliability and flexibility suggest its utility across various sectors where the integrity of random number sequences is crucial.</p>
      </abstract>
      <kwd-group>
        <kwd>eol&gt;PRNG</kwd>
        <kwd>source identification</kwd>
        <kwd>hybrid neural network</kwd>
        <kwd>RNN</kwd>
        <kwd>CNN</kwd>
        <kwd>cryptography</kwd>
        <kwd>machine learning</kwd>
        <kwd>classification</kwd>
        <kwd>data security 1</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>Identification of the source of (pseudo) random numbers is
an important task in many areas of modern IT management.
In the spheres where random numbers are used in
cryptography [1], modeling, communication [2], statistical
analysis [3], medicine [4], game industry accurately
identifying the source of these numbers becomes
fundamental to ensuring the security and reliability of
systems. Random number generators play a critical role in
these processes, and their vulnerability or incorrect
operation can have large-scale negative consequences for
many applications, including data security and the stability
of financial systems [5].</p>
      <p>
        The relevance of research on the identification of
sources of random numbers is due to the growing number
and complexity of attacks that can exploit weaknesses in
random number generators. Reliable classification and
identification of HVC is a necessary condition for ensuring
the appropriate level of security and stability of information
systems [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ].
      </p>
      <p>
        This paper proposes a model for identifying sources of
random numbers based on the use of a hybrid neural
network. The developed model makes it possible to
systematically approach the recognition of the
characteristics of various random number generators,
taking into account their unique statistical properties, and
to develop effective strategies for increasing the accuracy of
identification [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ].
      </p>
      <p>
        To achieve a high level of accuracy in the identification
of sources of random numbers, the paper discusses the key
stages of the developed model, including the architecture of
a hybrid neural network, the use of different generators for
training the model, as well as the analysis of classification
results. The described approach allows researchers and
practitioners to adapt existing techniques to the specifics of
their tasks, thus providing more effective risk management
and increasing the reliability of systems using random
numbers [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ].
      </p>
      <p>
        Research in the field of identification of random number
sources is actively developing thanks to the use of machine
learning methods and neural networks. Below is an analysis
of several key works in this field [
        <xref ref-type="bibr" rid="ref9">9</xref>
        ].
      </p>
    </sec>
    <sec id="sec-2">
      <title>2. Approaches to the generation of random numbers</title>
      <p>
        Having analyzed modern approaches to the generation of
random numbers [
        <xref ref-type="bibr" rid="ref10">10</xref>
        ], we will focus in more detail on the
following approaches:
      </p>
      <p>
        1. Using neural networks to generate random numbers:
One of the newest approaches is the use of neural networks
to generate pseudorandom numbers. For example, the work
of Jeong et al. (2018) uses an LSTM network to generate
0000-0002-2835-4279 (D. Proskurin); 0000-0001-9036-6556
(T. Okhrimenko); 0000-0003-4992-0564 (S. Gnatyuk);
0000-0003-06462823 (D. Zhaksigulova); 0000-0003-2908-970X (N. Korshun)
© 2024 Copyright for this paper by its authors. Use permitted under
Creative Commons License Attribution 4.0 International (CC BY 4.0).
pseudorandom numbers, which demonstrates the
possibility of using neural networks to generate sequences that
approximate the properties of true random numbers [
        <xref ref-type="bibr" rid="ref11">11</xref>
        ].
      </p>
      <p>
        2. Hybrid approaches and their effectiveness: In a study
conducted by Akhshani et al. (2014), a pseudo-random
generator based on quantum chaotic mapping is presented,
demonstrating the effectiveness of hybrid models for
random number generation. The use of such models allows
obtaining high-quality sequences, which is important for
cryptographic applications [
        <xref ref-type="bibr" rid="ref12">12</xref>
        ].
      </p>
      <p>
        3. With the use of logistic maps: The work of Wang et al.
(2016) investigates the use of a fragmented logistic map for
pseudorandom number generation, which shows high
performance compared to traditional methods. This
emphasizes the importance of choosing the right algorithm
for specific random number generation tasks [
        <xref ref-type="bibr" rid="ref13">13</xref>
        ].
      </p>
      <p>
        4. Use of chaotic systems: A study by Merah et al. (2013)
considers the generation of pseudo-random numbers based
on the chaotic Chua’s Circuit system, which allows for
achieving high reliability and security. Chaotic systems
provide high entropy, which is critically important for
cryptographic applications [
        <xref ref-type="bibr" rid="ref14">14</xref>
        ].
      </p>
      <p>
        The analysis of recent studies [
        <xref ref-type="bibr" rid="ref13">13</xref>
        ] shows that the use of
neural networks, especially hybrid models, is a promising
direction for the identification and generation of
pseudorandom numbers. These approaches allow for high accuracy
and reliability, which is important for many applications,
including cryptography and simulations [
        <xref ref-type="bibr" rid="ref15">15</xref>
        ].
      </p>
      <p>Further research may focus on improving these
methods, including the integration of additional
regularization elements and the development of new neural
network architectures that will provide even higher quality
and reliability of random number generation.</p>
    </sec>
    <sec id="sec-3">
      <title>3. A model of PRNG identification using a hybrid neural network</title>
      <p>The developed model (Fig. 1) for identifying the source
of random numbers consists of the following stages:</p>
      <p>1. Data preparation: At this stage, it is necessary to
collect and prepare sequences of random numbers
generated by various Random Number Generators (RNGs).</p>
      <p>
        Sequences are divided into blocks of 10 elements to ensure
the same length of input data. Each sequence is labeled with
a corresponding generator label [
        <xref ref-type="bibr" rid="ref16 ref17 ref18">16–18</xref>
        ].
      </p>
      <p>Next 8 generators were used:</p>
      <p>An identically seeded dataset of 4000 sequences was
generated for each generator, except for MS, where 200
sequences were generated (Fig. 2).</p>
      <p>Quality
Average. Although the generator is fast and has high entropy, the deviation from a uniform
distribution is signi icant.</p>
      <p>High. The generator is very fast and has high randomness and low autocorrelation.
High. The generator is fast, has high randomness, and very low autocorrelation.
Low. The generator has lower randomness and high autocorrelation.</p>
      <p>Low. The generator has very low randomness and high autocorrelation.</p>
      <p>High. The generator is fast and has high randomness and low autocorrelation.
Low. Despite the speed and high randomness, the very high autocorrelation is a serious
drawback.</p>
      <p>High. The generator is fast, has high randomness, and very low autocorrelation.
2. Construction of a hybrid neural network: At this stage, a
hybrid neural network is created that combines Recurrent
Neural Networks (RNN) and Convolutional Neural
Networks (CNN). Such an architecture allows efficient
processing of data sequences, taking into account both
temporal dependencies and local patterns. The components
of the network architecture, their functions, and
interactions are discussed in detail below.</p>
      <p>Recurrent neural networks specialize in processing
sequences of data and storing information about previous
elements of the sequence. This allows the model to detect
temporal dependencies, which is critical when analyzing
random numbers.</p>
      <sec id="sec-3-1">
        <title>Main components of RNN:</title>
        <p>

</p>
        <p>Input layer: Accepts sequences of random
numbers divided into blocks of 10 elements.</p>
        <p>Hidden layers: Several hidden layers of RNN allow
the model to store and process information about
previous states. The following types of RNNs are
used in our architecture:
LSTM (Long Short-Term Memory): Provides
longterm memory by storing information about
previous elements of a sequence for a long time.
LSTM layers are used to detect complex temporal
dependencies.
GRU (Gated Recurrent Unit): A lighter version of
LSTM that keeps the important information and
forgets the unnecessary, which increases the
efficiency of the model.</p>
        <p>Output layer: Transfers the processed information
to the next component of the architecture—
convolutional neural networks.</p>
        <p>Softmax layer: The final layer uses the Softmax
function to provide a probabilistic output that
allows the model to classify the input data into one
of eight classes (random number generators).</p>
        <p>A hybrid approach combining RNN and CNN has
several key advantages:</p>
      </sec>
      <sec id="sec-3-2">
        <title>RNN parameters:</title>
        <p>The number of layers: Three LSTM layers with
128, 64, and 32 neurons respectively.</p>
        <p>Activation functions: ReLU and Sigmoid functions
are used to ensure non-linearity and stability of
learning.</p>
        <p>Dropout: Regularization with a value of 0.2 to
prevent overtraining.</p>
        <p>3. Convolutional Neural Networks (CNN): Convolutional
neural networks are used to detect local patterns in data.
They effectively highlight features at different levels of
abstraction, which increases classification accuracy.</p>
        <p>Main components of CNN:















</p>
      </sec>
      <sec id="sec-3-3">
        <title>CNN parameters:</title>
      </sec>
      <sec id="sec-3-4">
        <title>Connecting layer:</title>
        <p>Convolutional layers: Use filters to detect local
patterns in data. Each filter moves through the
input, highlighting certain features (for example,
changes in sequences of numbers).</p>
        <p>First convolution layer: 64 3×3 filters, ReLU
activation function.</p>
        <p>Second convolution layer: 128 3×3 filters, ReLU
activation function.</p>
        <p>Pooling layers: Reduce the dimensionality of the
data, preserving the most important features.</p>
        <p>MaxPooling is used with a window size of 2×2.</p>
        <p>Normalization layers: Used to stabilize the
learning process by normalizing activations in
hidden layers.</p>
        <p>Number of layers: Two convolutional layers
followed by subsampling layers.</p>
        <p>Activation functions: Using ReLU to enforce
nonlinearity and improve the model’s ability to extract
important features.</p>
        <p>Dropout: Regularization with a value of 0.3 after
each convolutional layer to prevent overtraining.</p>
        <p>After processing the data in RNN and CNN, the
layers are combined to create a complete picture
of the input sequences.</p>
        <p>Flatten layer: Converts multidimensional data
from convolutional layers into one-dimensional
vectors ready for further processing.</p>
        <p>Dense (fully connected) layers: Two layers with 64
and 32 neurons, which allows the model to make
final classifications. The activation function is
ReLU.</p>
        <p>Taking into account temporal dependencies: RNN
layers allow the model to remember and take into
account previous values in the sequence.</p>
        <p>Detection of local patterns: CNN layers provide
detection of important local features in sequences,
which increases classification accuracy.</p>
        <p>Improved accuracy: The combination of the two
types of networks allows the model to take into
account both global and local characteristics of the
data, which significantly improves its
performance.</p>
        <p>4. Model training: At this stage, the effectiveness of the
trained model is evaluated on the test data set. Such metrics
as accuracy (accuracy), accuracy for each class (precision),
completeness (recall), and F1-measure are determined. The
results are compared with existing methods of random
number source identification to evaluate the merits of the
developed model. Metrics:</p>
        <p>Accuracy: Defined as the percentage of correctly
classified sequences among all sequences in the
test set. This is the main metric that shows the
overall performance of the model.</p>
        <p>Precision for each class (Precision): Determines
the percentage of correctly classified samples of a
certain class among all samples classified as this
class. This is a measure of classification accuracy
for each generator.</p>
        <p>Completeness (Recall): Determines the percentage
of correctly classified samples of a certain class
among all samples of that class in the test set. It is
an indicator of the model’s ability to detect all
samples of a certain class
F1-measure: Harmonic mean between precision
and completeness. It is an integrated metric that
balances accuracy and completeness.</p>
        <p>The hybrid neural network showed 87.14% overall
accuracy, being able to classify sequences from three
generators: LFSR, ACORN, and BBS with high accuracy (99–
100%) (Fig. 3 and Table 3).</p>
        <p>Accuracy: The overall accuracy of 87.14% indicates
the high efficiency of the hybrid neural network in
the classification of sequences of random numbers.</p>
        <p>The generators ACORN, BBS, and LFSR stand out,
for which the accuracy reaches 100%, 100%, and
99%, respectively.</p>
        <p>Accuracy for each class (Precision): Accuracy
varies for different generators. The high
accuracies for the ACORN and BBS generators
indicate that the model can correctly classify these
generators. For the MS generator, the accuracy is
significantly lower, indicating the difficulty of
classifying this generator due to high
autocorrelation.

</p>
        <p>F1-Measure: The high F1-Measure for the ACORN
and BBS generators confirms that the model
strikes a good balance between accuracy and
completeness for these generators. A low F1
measure for the MS generator indicates the need
to improve the model for that particular generator
(Table 4).</p>
        <p>The source has
been identi ied, %
63.75
71.25
69.75
99.00
100
100
60.00
67.00
statistical tests or simple machine learning
algorithms.</p>
        <p>Generalization ability: Thanks to the
combination of RNN and CNN, the model can
take into account both temporal dependencies
and local patterns, which provides a more
accurate classification for different types of
generators.</p>
        <p>Completeness (Recall): High recall for ACORN and
BBS generators (100%) indicates that the model can
detect all samples of these generators in the test
set. The low completeness for the MS generator
(60%) indicates that the model misses many
samples of this generator.</p>
        <p>Average. Although the generator is fast and has high entropy, the deviation from a
uniform distribution is signi icant
High. The generator is very fast, has high randomness and low autocorrelation
High. The generator is fast, has high randomness, and very low autocorrelation
Low. The generator has lower randomness and high autocorrelation
Low. The generator has very low randomness and high autocorrelation
High. The generator is fast, has high randomness, and low autocorrelation
Low. Despite the speed and high randomness, the very high autocorrelation is a
serious drawback</p>
        <p>High. The generator is fast, has high randomness, and very low autocorrelation
The proposed method for identifying sources of random
numbers based on a hybrid neural network
demonstrates significant advantages over existing
methods:
</p>
        <p>Higher accuracy: A hybrid neural network
provides higher classification accuracy
compared to traditional methods such as</p>
        <p>Flexibility: The model can be adapted to
different random number generators and used
in different contexts, including cryptography
and simulations.</p>
      </sec>
    </sec>
    <sec id="sec-4">
      <title>4. Conclusion</title>
      <p>The results of the model performance evaluation
confirm that the hybrid neural network is an effective
tool for identifying the sources of random numbers. The
model showed high accuracy for most generators, but
there are areas for improvement, especially for the MS
generator.</p>
      <p>Also, as a result of the research, the following tasks
were solved:



</p>
      <p>Existing approaches to the identification of
random number sources were analyzed,
including traditional methods and modern
approaches using neural networks. The
advantages and disadvantages of each of the
approaches are determined. The analysis
showed that although traditional methods
provide a basic level of identification, the use
of hybrid neural networks significantly
increases the accuracy and efficiency of
classification.</p>
      <p>A model of random number source
identification based on a hybrid neural RNN
and CNN layers has been developed. The
model includes pre-processing of the data,
development of the model architecture,
training of the model on the collected data, and
further evaluation. This allows taking into
account both temporal dependencies in
sequences and local patterns, which ensures
high accuracy of identification.</p>
      <p>The developed model was tested
experimentally on real data generated by
various HHFs. The obtained results confirmed
the high efficiency of the model, in particular,
the model showed an accuracy of more than
95% for such generators as BBS, ACORN, and
LSFR. However, areas for further improvement
were identified, particularly for the XS, MT,
CC20, LCG, and MS generators, where
accuracy was lower. This emphasizes the need
for further research and improvement of the
model.</p>
      <p>Regularization: Implementing additional
regularization techniques, such as Dropout or
Batch Normalization, to improve the model’s
ability to generalize data.</p>
      <sec id="sec-4-1">
        <title>Further areas of research:</title>
        <p>

</p>
        <p>Parameter optimization: Conducting
additional experiments with various
hyperparameters of the model to achieve
optimal accuracy.</p>
        <p>Data Analysis: The study of various data
processing techniques, such as normalization
or standardization, to improve the quality of
the input data.</p>
        <p>Data set expansion: Inclusion of additional
random number generators to provide a more
comprehensive assessment of model
performance.</p>
        <p>The study demonstrates the potential of hybrid
neural networks in the tasks of identifying sources of
random numbers. The next steps will include refining
the model architecture, implementing additional
regularization techniques, and optimizing the
hyperparameters to further improve accuracy and
robustness.</p>
      </sec>
    </sec>
    <sec id="sec-5">
      <title>Acknowledgment</title>
      <p>This work was supported by the Shota Rustaveli
National Foundation of Georgia (SRNSFG)
[NFR-2214060] as well as the Ministry of Education and Science
of Ukraine (grant #0122U002361 “Intelligent system of
secure packet data transmission based on
reconnaissance UAV”).</p>
    </sec>
  </body>
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