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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Method  of  Calculation  of  Information  Protection  from  Clusterization Ratio in Social Networks </article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Vitalii Savchenko</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Volodymyr Akhramovych</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Oleksander Matsko</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Ivan Havryliuk</string-name>
          <email>ivan.havryliuk@gmail.com</email>
        </contrib>
      </contrib-group>
      <abstract>
        <p>   The article investigates the dynamic models of the information protection system in social networks taking into account the clustering coefficient, and also analyzes the stability of the protection system. In graph theory, the clustering factor is a measure of the degree to which nodes in a graph tend to group together. The available data suggest that in most real networks, and in particular in social networks, nodes tend to form closely related groups with a relatively high density of connections; this probability is greater than the average probability of a random connection between two nodes. There are two variants of this term: global and local. The global version was created for a general idea of network clustering, while the local one describes the nesting of individual nodes. There is a practical interest in studying the behavior of the system of protection of social networks from the value of the clustering factor. Dynamic systems of information protection in social networks in the mathematical sense of this term are considered. A dynamic system is understood as any object or process for which the concept of state as a set of some quantities at a given moment of time is unambiguously defined and a given law is described that describes the change (evolution) of the initial state over time. This law allows the initial state to predict the future state of a dynamic system. It is called the law of evolution. The study is based on the nonlinearity of the social network protection system. To solve the system of nonlinear equations used: the method of exceptions, the joint solution of the corresponding homogeneous characteristic equation. Since the differential of the protection function has a positive value in some data domains (the requirement of Lyapunov's theorem for this domain is not fulfilled), an additional study of the stability of the protection system within the operating parameters is required. Phase portraits of the data protection system in MatLab / Multisim are determined, which indicate the stability of the protection system in the operating range of parameters even at the maximum value of influences.</p>
      </abstract>
      <kwd-group>
        <kwd> 1  dynamic models</kwd>
        <kwd>information protection system</kwd>
        <kwd>social networks</kwd>
        <kwd>clustering coefficient</kwd>
        <kwd>nonlinearity</kwd>
        <kwd>exception method</kwd>
        <kwd>homogeneous characteristic equation</kwd>
        <kwd>function differential</kwd>
        <kwd>system stability</kwd>
        <kwd>phase portrait</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction </title>
      <p>
        Descriptions of dynamical systems for various
problems depending on the law of evolution are
specific form of the mathematical model of the
corresponding dynamic system [
        <xref ref-type="bibr" rid="ref1">3</xref>
        ].
      </p>
      <p>The mathematical model of a dynamic system
is considered to be given if the parameters
(coordinates) of the system are introduced, which
unambiguously determine its state, and the law of
evolution is specified. Depending on the degree of
approximation to the same system, different
mathematical models can be matched.</p>
      <p>Theoretical study of the dynamic behavior of a
real object requires the creation of its
mathematical model. In many cases, the
procedure for developing a model is to compile
mathematical equations based on physical laws.
Usually these laws are formulated in the language
of differential equations. As a result, the
coordinates of the state of the system and its
parameters are interconnected, which allows us to
begin to solve differential equations under
different initial conditions and parameters.</p>
    </sec>
    <sec id="sec-2">
      <title>2. Related works </title>
      <p>
        In the article [1] the definition of the clustering
coefficient in the case of (binary and weighted)
directional networks is extended and the expected
value for random graphs is calculated. In [2], it is
noted that the properties of the small world of
neighboring connections are higher than in
comparative random networks. If a node has one
or no neighbors, in such cases the local clustering
is traditionally set to zero, and this value affects
the global clustering factor. It is proposed to
include the coefficient θ for isolated nodes in
order to estimate the clustering coefficient, except
in cases from the determination of Watts and
Strogats. In [
        <xref ref-type="bibr" rid="ref1">3</xref>
        ] a method of determining trust and
protection of personal data in social networks was
developed. In article [
        <xref ref-type="bibr" rid="ref2 ref3 ref4">4-6</xref>
        ] the clustering
coefficients for social networks, including power
ones, are considered. In [
        <xref ref-type="bibr" rid="ref5">7</xref>
        ], a comparison of
different generalizations of the clustering
coefficient and local efficiency for weighted
undirected graphs is made. In the article [
        <xref ref-type="bibr" rid="ref6">8</xref>
        ] the
analysis of the clustering coefficient on the social
network twitter is carried out. In [
        <xref ref-type="bibr" rid="ref7">9</xref>
        ], an analysis
of the clustering coefficient through triads of
connections was performed. In the article [
        <xref ref-type="bibr" rid="ref8">10</xref>
        ] the
dependence between the clustering coefficient
and the average path length in a social network is
investigated. In [
        <xref ref-type="bibr" rid="ref9">11,13</xref>
        ] the use of clustering
methods of social networks for personalization of
educational content is investigated. The article
[12,15] discusses the behavior of the clustering
coefficient for complex networks. In [14], it was
concluded that based on the results of the
experiment, it can be concluded that among the
clustering algorithms there is no universal
algorithm that would be significantly ahead of
others on all data sets. The leaders of
benchmarking are the algorithms Spinglass and
Walktrap. From the considered analysis of the
works, it can be concluded that currently the
protection of users in social networks is
considered primarily as a technical problem that
does not take into account the structural
parameters of the network and its topological
features. This emphasizes the relevance of the
topic of work regarding the construction of a
protection system based on structural parameters,
taking into account network clustering.
      </p>
    </sec>
    <sec id="sec-3">
      <title>3. Formulation of the research task </title>
      <p>It is necessary to investigate the dynamic
system of information protection in the social
network (SN) from the clustering factor. Carry out
modeling of a nonlinear protection system taking
into account the clustering factor in SN.
Investigate the stability of the protection system
in the SN.</p>
    </sec>
    <sec id="sec-4">
      <title>4. Main part </title>
    </sec>
    <sec id="sec-5">
      <title>4.1. Nonlinear  solution  of  the </title>
      <p>protection  system  in  the  SN, 
taking into account the action of 
a  specific  parameter  ‐  the 
clustering factor </p>
      <p>
        Analysis of graphical dependences of a linear
system [
        <xref ref-type="bibr" rid="ref1">3</xref>
        ] indicates the nonlinearity of the
system. Therefore, in the system of equations (1)
we introduce nonlinear components (2):
 ddIt  Z p Z  (Cv  СK ) I

 dZ   ( vV Cv1
 dt N 2
) I (Cd 2  Cd 1 )
(1)
where:  Cv1 - the total number of connections
vV
in the network, N - the number of vertices in the
network.
ZpZ(Cv СK )I L2(I2)L3(I3)...
      </p>
      <p>)I (Cd 2Cd1)К2(Z2)K3(Z3)...
(2)
where: L2 , L3 , etc. K2 , K3 , etc. some linear
operators. We consider the nonlinearity of the
system to be weak, which allows us to find a
solution for each equation of the system (2) by the
method of successive approximation, putting:</p>
      <p>I  I1  I2  I3...
Since the differential of the protection function
has a positive value in some data domains (the
requirement of Lyapunov's theorem for this
domain is not fulfilled), an additional study of the
stability of the protection system within the
operating parameters is required</p>
      <p>Z  Z1  Z2  Z3  ...</p>
      <p>Let at
dI  0 , dI  0, and dZ  0 , dZ  0</p>
      <p>dt dt
I  I0 Sint, Z  Z0 Sint</p>
      <p>We obtain a system of equations:

dI ZpZ(CvСK )IL2(I02Sin2t )
dt

L3(I03Sin3t )...
  Cv1
ddZt( vVN2
K3(Z03Sin3t )...</p>
      <p>)I (Cd 2Cd1)К2(Z02Sin2t )</p>
      <p>Let's rewrite the system and present it as
follows:
 dI  Z  1I   Lk I0k sin k  t ,
 dddZtt   2 I   kk22K k Z 0k sin k  t ,
where:
  Zp , 1  Cv  CK , 2  Cd2Cd1 ,   (
Next, use the exception method:
dZ
dt
  2 I   


k 2</p>
      <p>Kk Z0k sink  t 
1  d2Z 1  </p>
      <p> kKk Z0k sink1t cost   (5)
2  dt2   k2 
(3)
(4)
 Cv1
vV</p>
      <p>N2 )</p>
      <p>Substitute all the found expressions (5) in the
first equation of system (4):
1 d2Z 1  
2  dt2 k2kKkZ0k sink1tcost </p>
      <p>   
Z  1 dZ   K Zk sinkt 
2  dt k2 k 0 </p>
      <p>
 k  2 Lk I0k sin k  t
d2Z dZ
dt2  1 dt  2Z 

1 </p>
      <p> kKkZ0k sink1t cost 
 k2</p>
      <p>
1  1k2 KkZ0k sink t </p>
      <p>
 2 k2 Lk I0k sink  t
(6)
(7)</p>
      <p>Now we find a common solution of the
corresponding homogeneous equation:</p>
      <p>Z  1Z  2Z  0
(8)</p>
      <p>The characteristic equation has the form:
 2  1  2  0 . Consider the case of the
positive discriminant of this equation:</p>
      <p>2
D  1  4 2  0  1,2 
1  12  4 2</p>
      <p>Zодн (t)  c1e
joint solution of a homogeneous equation.</p>
      <p>To find the general solution of the
inhomogeneous equation we use the method of
variation of arbitrary constants:</p>
      <p>Zодн (t)  c1(t)e
where: c1(t), c2 (t) are from the system:
c1 (t)e1 12242 t


c (t)1 1242 e


 1 2


c2(t)1 12242 e
c2(t)e1 12242 t 12  42  N(t)
c2(t) 
c1(t) </p>
      <p>1
12 42</p>
      <p>1
N(t)e
(16)</p>
    </sec>
    <sec id="sec-6">
      <title>3.2.  Define  the  phase  portrait  of  the  data protection system </title>
      <p>Initial equation:
d2Z dZ 1  kKkZ0k sink1tcost 
dt2  1 dt 2Z   k2</p>
      <p> 
1  1k2 KkZ0k sinkt  2k2 LkI0k sinkt
(17)</p>
      <p>The solution will be implemented in the
program MatLab / Multisim. Let's make the
scheme (Fig. 7).</p>
      <p>The phase portrait is presented in the form of
an ellipse, which indicates the stability of the
personal data protection system.</p>
      <p>The results of the program are presented in
Fig. 8, 9.
Figure 10: Harmonic oscillations of the 
protection system on time Z=f(t) taking into 
account the attacks 
 
 
Figure 11: Phase portrait of the protection 
system on clustering factor taking into account 
the attacks </p>
    </sec>
    <sec id="sec-7">
      <title>5. Analysis of the obtained results </title>
      <p>In contrast to previous research by scientists, it
has been proven that the SN protection system is
stable even from external maximum influences
and a specific parameter of the clustering
coefficient in the operating range of parameters.</p>
    </sec>
    <sec id="sec-8">
      <title>6. Conclusions </title>
      <p>For the first time in the article the dynamic
model of the information protection system in
social networks is investigated taking into account
the clustering coefficient, and also the analysis of
the stability of the protection system is carried out.
A nonlinear equation of information protection is
obtained. It is shown that the protection index
changes depending on the clustering coefficient.
Phase portraits of the protection system are
obtained, which indicate the resistance of the
system to external influences and the clustering
coefficient in SN.</p>
    </sec>
    <sec id="sec-9">
      <title>7. References </title>
      <p>[1] Giorgio Fagiolo. Clustering in complex
directed networks. Phys Rev E Stat Nonlin
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Aug 16.
[2] Marcus Kaiser (2008). Mean clustering
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arXiv:0802.2512.
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