V5-Secure Interdependent Networks for Peer-to-Peer and Online ...

Secure Interdependent Networks for Peer-to-Peer and Online Social Network Qiyi Han, Hong Wen, Gang Feng, Longye Wang, Fei Pan National Key Laboratory of Science and Technology on Communication University of Electronic Science and Technology of China, Chengdu, China [email protected], [email protected], [email protected], [email protected], [email protected]

Abstract—Peer-to-peer (P2P) systems and online social network (OSN) both have achieved tremendous success. Recent studies suggest that the cooperation of P2P and OSN can achieve better efficiency and security. Unfortunately, novel security problems are emerging as the mutual cooperation and dependence contributes to forming the interdependent networks which are more vulnerable for malicious attack as well as rumor propagation. In this paper, we examined the security environment for P2P and OSN, respectively, and analyzed the security problem derived from the cooperation and interdependence of two networks. The spreader-ignorant-recaller-stifler (SICR) is leveraged to model the rumor spreading in the interdependent networks. In order to enhance the security, we proposed two security schemes named authentication intervening and splitting target and their performance summaries indicate to be effective, simple, and potentially transformative way to guarantee the security for interdependent networks of P2P and OSN. Keywords—Peer-to-peer (P2P); online social network (OSN); security; interdependent networks; rumor

I. INTRODUCTION The Peer-to-peer (P2P) systems have shown convenience and efficiency for internet users. Concretely, it entails prevailing popularity of P2P systems, e.g. file sharing, E-commercial, and distributed computing [1-2]. P2P technologies also can be used for LTE self organizing networks, which is defined in the 3GPP standard [3]. P2P technologies will undoubtedly become more and more important in 5G networks. However, Security is a critical restriction for the progressing of P2P systems. Recently, researchers [1-2] suggest that long-term relationships among file sharing peers of the P2P systems could be explored to achieve better sharing efficiency and security. In the same time, the explosive growth of online social network (OSN) applications e.g. Facebook and Twitter, which maintain the social relationships in long-

term, sheds new light into this problem. OSN exploit the social intercourse in an easy and convenient way by enabling users to share and contribute much more than what they can in real life such as posting a video or picture on their profile page or simply share files with no real interactivity among users. In particular, it is noticed that a number of Bit-Torrent, which is an application of P2P, swarms are now triggered by Twitter, reflecting a new trend for initializing sharing among communities [2]. On the other hand, OSN is witnessed to take advantage of P2P to develop file sharing and E-commercial activities [4]. The P2P systems can help the OSN in large data transmission and in privacy with strangers or short-term interaction. P2P systems and OSN are becoming closely cooperation and increasingly dependent on each other. The mutual cooperation and dependence contributes to forming the interdependent networks [5-7]. However, security problems are arising when these two technologies contribute together with each one bringing in their own security issues. The existing security strategy use the complex network theory [6-7] and access control [8-9] to improve the robustness and privacy of interdependent networks which have relatively static topology. However, these strategies are not suitable for P2P and OSN as the features of autonomy and dynamic make the topology of P2P and OSN unable to design or manage. In P2P and OSN, the main security challenge is not node failure but trust crisis [1][10] and privacy disclosure [11-12], respectively. Moreover, malicious attacks in one application often traverse to other dependent applications and possibly even back to the application which contribute to worse consequence. From this view, we examined the security environment for P2P and OSN, respectively and analyzed the security problem derived from the cooperation and interdependence of two networks. Then a spreading dynamics, named spreader-ignorant-recaller-stifler (SICR), is leveraged to

model the rumor spreading in the interdependent networks. In order to enhance the security, two security schemes named authentication intervening and splitting target are proposed. Their performances indicate to be effective, simple and potentially transformative way to guarantee the security for interdependent networks of P2P and OSN. The rest of the paper is organized as follows. Section II indicates the security issues in P2P and OSN. The analysis of the interdependent security threats is given in Section III. In Section IV and V, the static and dynamic models of malicious attacks are given, respectively. Security schemes are proposed in Section VI. Finally, we conclude the paper in Section VII. II. THE SECURTIY ENVIRONMENT FOR INDIVIDUAL P2P AND OSN NETWORKS As shown in Fig.1, P2P and OSN are parallels, and both are typical complex networks [10][13][14]. It is found that most topology of these complex networks have three main properties i.e. small world, scale free and high clustering. P2P and OSN have many similarities. OSN is even considered as one application of P2P. However, the boundaries between P2P and OSN are still very solid, especially in security environment.

Fig. 1 P2P and OSN A. P2P securtiy analysis The distributed, open and anonymous natures of P2P raise several issues. Firstly, P2P is a distributed network without central server or global view to obtain network management. Secondly, the open nature allows users to join and leave the P2P system at ease. Therefore, the network topology is dynamic all the time. Most users are dealing with one another unrelated strangers. Finally, the

anonymous nature leaves users take no accountability for the content sharing on the network which opens the door to abuse the network by malicious and irresponsible peers. As a result, the users as not expecting to have high secure experience without any trust on each other in P2P networks. Aimed at afore mentioned issues, the most important thing is exploiting trust relationship [10]. It can help a user make wise decision to select partner with higher reputation for performs a more secure transaction. Even so, novel malicious behaviors [15] emerged and still brought damages to threaten the P2P security. B. OSN securtiy analysis OSN provides a virtual community for people interested to interact with each other. On contrast with P2P, OSN maintain long-term relationship. Recently researchers [1] suggest that long-term relations are reliable and secure to build trust model. However, OSN suffer greatly from human derived issues. Owing to the unaware nature of many users towards security or trust, simple social engineering attacks can capture a user’s sensible information [4]. Moreover, the social sharing, such as photos and video, involved in privacy information are spreading without consciousness. Although it does not require proclaim names or identity, privacy information exposure is inevitable when users participate in social communities. Such behavior is a double-edged sword [4]. There are inherent design conflicts between privacy and utility in data publishing. III. THE SECURITY ENVIRONMENT FOR INTERDEPENDENT P2P AND OSN NETWORKS In this paper, we try to enhance OSN security by building upon the P2P architecture to OSN. The main concern in this architecture is the trust between nodes. Due to its fully distributed nature, the P2P architecture inherently avoids centralized control by any potentially malicious service provider. In order to cope with the lack of trust and lack of cooperation that are akin to peer to peer systems and to assure basic privacy among the users of the social network, we can leverage the trust relationships that are part of the social network application itself. The security functioning of P2P depends on the trust relations of OSN, and vice versa, the privacy-preserving of OSN depends on anonymous approach of P2P. In addition to security cooperation, it is witnessed the popularity that P2P and OSN are overlapped and provide service mutually. Therefore, there is an interdependent cooperation opportunity between P2P and OSN, e.g. P2P leverage the trust relationships that are inherent part of OSN, while OSN achieve privacy through distributed and anonymous P2P

systems. The cooperation contributes to novel interdependent networks which are quite different from the traditional infrastructure systems [5-7] whose critical security issue is cascade failures. That is a node failure in one network may lead to failure of dependent nodes in other networks. What is even worse, this node failures may happen recursively and result in a catastrophic cascade of failures [5]. The novel interdependent networks are stronger to face node failure but weaker to malicious attack and rumor propagation.

security mechanism, including trust model [1] and privacypreserving [11-12], can be avoided. In this way, both social relations and file sharing links can be adopted optionally to spread malicious attacks. On contrast with a single network, it contributes to significantly larger damage and makes the security environment more vulnerable. IV. THE STATIC CHARACTERISTICS OF INTERDEPENDENT NETWORKS

In this section, we will analyze the influence of static interdependent networks under intentional attack. A. Intentional attak As mentioned, P2P and OSN are both scale-free (SF) networks which differ from the regular network of power grid. For SF-SF interdependent networks, the degree follows power-law distributions:

P(k ) = PP 2 P (k ) = POSN (k ) ∝ k −γ , 2 < γ ≤ 3

Fig. 2 Interdependent networks model Considering the interdependent networks model shown in Fig.2, there are two networks, i.e. P2P and OSN respectively, with the same number of nodes. The edges in P2P and OSN are different because each network is connected differently. The edges in P2P denote the links of file sharing or transactions, while the edges in OSN denote the social relations. We denote such dependence by a bidirectional link that defines a one-to-one correspondence between nodes of P2P and OSN. As there are two networks, the interdependent networks for P2P and OSN are facing two-side malicious attack. Practically, there are no security mechanism between P2P and OSN. The existing researches [1-2] assumed that cooperation between the two networks are based on inherently trust and dependence without any protection. With this assumption, malicious attacks in one application can easily traverse to other dependent applications which contribute to a first-order phase transition, quite different from a second-order phase transition such as that characterizing percolation of a single network. For example, once a P2P node is captured by malicious attack, the corresponding OSN node can be captured easily. Therefore, one successful attack can capture two nodes. What is even worse, it suffers from rumor propagation. The catastrophic impact will propagate both in P2P layer and OSN layer. Owing to the dependence between the networks, the

(1)

The SF networks are robust to random attack but vulnerable to intentional attack. The intentional attack is defined as following. The weight of a node is defined as:

wa = wA = (kaP 2 P + k AOSN ) β

(2)

where ka denotes the degree of P2P node

a , k A denotes

A , β denotes the attack strength. Assumed that there are N pairs of nodes in the

the degree of OSN node

interdependent networks and one pair of nodes will be attacked each time. Then the probability of being attacked is w (3) Wβ (kaP 2 P , k AOSN ) = N a ∑ wi i =1

According to formula (3), nodes with higher degree have a larger probability to be attacked. Suppose that the nodes suffer ergodic attack at a rate (1 − p )(0 < p < 1) recursively until N (1 − p ) pairs of nodes are captured, numerically, more than 95% nodes will be insulated when less than 10% nodes are captured by intentional attack. B. Influence analysis As interdependent networks suffer intentional attack, we leverage the percolation theory [5] to convert the intentional attack into random attack so as to analyze the influence. When (1 − p ) part of nodes is captured in the initial stage, the remaining degree distribution of the last p nodes is:

P(k ) pN

Pp ( k ) =

(4)

Suppose N → ∞ , the derivation of formula (4) is:

−p

d ( Pp (k ))

Pp (k ) w p

= Pp (k ) −

(5) < (k ( p )) β > where < (k ( p )) β >= ∑ Pp ( k ) w p . Given the generating

dp

function:

Gβ = ∑ P (k ) x p , f = Gβ−1 ( p ) , w

k

then:

Pp (k ) = P (k )

f

wp

Gβ ( f )

=

1 w P(k ) f p p

(6)

Pp (k ) is:

The generating function of

G p ( x ) = ∑ Pp (k )x k = k

1 w ∑ Pp (k ) x k f p p k

(7)

rumors are unreliable information, e.g. virus, Trojan, fraud, and slander. In order to enhance the security, it is necessary to study the virus propagation mechanism. Here, we leverage the SICR [14] to model the rumor spreading in the interdependent networks. At the effect of bidirectional link, the two interdependent nodes are considered as one node in the rumor spreading model, as shown in Fig. 3. Contrast with the traditional SIR model [14], there are diversities in the interdependent networks. Considering the situation that there are some ignorant who may be inspired by some incentives to continue spreading rumors. For instance, when a user heard about a rumor in P2P, he decided to refuse to spread it. Then he performed as a stifler. However, faced with increasing rumors propagated by friends’ links in OSN, he may turn to convince of the rumor and began to spread it as a spreader. That is to say some stiflers are not in dormant state of rumor terminator and when conditions permit they will revive.

Then the issue of intentional attack converts to random attack:

pɶ Gɶ o = G p (1 + ( x − 1)) p

∑ P (k )kf ∑ P (k )k

(8)

wp

where

pN < k ( p) > pɶ = = N

p

k

denotes

the

p

k

removed links accounted for the proportion of the total links. According to the percolation theory [5], when the cluster is not further fragmented, the whole networks are met as:

 x = g P 2P ( y) p   y = gOSN ( x) p

(9)

where g P 2 P ( p) = 1 − Gɶ 0 (1 − p(1 − f P 2 P )), Gɶ1 ( x) = Gɶ 0' ( x) Gɶ '0 (1) . If p is large enough, there also exists a solution such that the giant mutually connected component is of non-zero size. We can easily exclude y from these equations and obtain a single equation:

x = g P 2 P ( gOSN ( x ) p ) p

dg dg P 2 P [ pgOSN ( x)] OSN ( x) dx dx

In the proposed model, we have four states including ignorant (I), spreader (S), recaller (C) and stifler (R). The contact and transition among the participants are given in Fig. 4. The rumor spreading model can be described as follows.

(10)

To derivative equation (10), finally, the critical condition of whole networks failure is:

1 = p2

Fig. 3 Rumor spreading links in interdependent networks

x = xc , p = pc

β α

(11)

V. RUMOR DYNAMICS IN THE INTERDEPENDENT NETWORKS If any information circulates without officially publicized confirmation, it is called rumor. In other words,

λ

ω

δ

Fig. 4 Structure of SICR

When a spreader contacts with an ignorant, the ignorant may believe the rumor and become a spreader at a rate λ or may not believe it and immediately become a stifler at a rate β , here λ + β ≤ 1 . When a spreader contacts with a stifler, the spreader becomes a stifler at a rate α . When a spreader contacts with another spreader, the initiating spreader becomes a recaller at a rate ω . When a recaller contacts with a spreader, the recaller becomes a spreader at a rate

δ

. Considering the normalization condition:

ρ (t ) + ρ s (t ) + ρ c (t ) + ρ r (t ) = 1 , i

The bidirectional link between the interdependent nodes achieves the cooperation between P2P and OSN while the malicious attack can use the bidirectional link to capture the other node easily. The key point to increase the security of the interdependent networks is to shield the other node from malicious attack by corresponding captured node. As the rumor is insulated in only one layer of interdependent network, the damage can be controlled in an acceptable level by the security functioning in the other dependent network. From this view, two security schemes are proposed, i.e. authentication intervening and splitting target.

The model can be described as follows:  d ρ i (t ) i s  dt = −(λ + β )kρ (t ) ρ (t )  s (12)  d ρ (t ) i s s s s r c s  dt = λ k ρ (t ) ρ (t ) − ω kρ (t ) ρ (t ) − α kρ (t ) ρ (t ) + δ k ρ (t ) ρ (t )  c  d ρ (t ) = ω kρ s (t )ρ s (t ) − δ k ρ c (t ) ρ s (t )  dt  r  d ρ (t ) = β kρ i (t ) ρ s (t ) + α k ρ s (t ) ρ r (t )  dt

From above description, we conclude as followings.

λ

reflects the infected ability of rumor. β and α reflect security mechanism.

ω and δ respectively reflect the security and vulnerability between the interdependent nodes. As above discussion, there are ways to restrict the rumor spreading and enhance the security. First one is to increase β and reduce

λ , i.e. each user should improve the

security awareness and prevent to be infected by rumor. This requires users to adopt security measures such as antivirus software, novel trust model [1][4] and privacy preserving [11-12]. Second one is increase α , i.e. security management should be deployed to restrict the rumor spreading and control the damages when suffer infection, such as protect the key nodes and stroke smart lost [6-7]. However, an authority organization is needed to manage the global situation which is hard to assign in either P2P or OSN. Third one is to regulate the ω and δ , i.e. manage or degrade the interdependent relationships to enhance the security between the interdependent nodes which is highlighted in next section. VI. SECURITY STRATEGY In addition to the existing security mechanism [6-7] that are suitable for networks with relatively static topology. Considering the specific circumstance of P2P and OSN, novel security schemes should be designed to aim at the interdependence.

Fig. 5 Security scheme Authentication Intervening The scheme is to insert an authentication system between the interdependent nodes, as shown in Fig. 5(b). With the authentication system, the authorized cooperation between two interdependent nodes can be achieved without any trouble. However, the unauthorized operations such as malicious attack are blocked. In this way, the parameter ω of rumor spreading is restricted. No more worrying about the malicious attack from the dependence node, the other node only needs to shield itself from attack in its located network. Then the existing dependence security mechanism, such as SocialTrust [1] and Privacy-preserving [11], can functioning to protect the interdependent networks. Splitting Target The scheme is to split the bidirectional link between the interdependent nodes into two unidirectional links. Generally, considering the social relations in long-term are more important than file sharing links, then we assign one OSN node and two P2P nodes as shown in Fig. 5(c). The interdependent relationship between two nodes is no more maintained. Given two unidirectional dependences, the cooperation between P2P and OSN still takes effect, but the malicious attack from the dependence node is limited in unidirectional link. For example, deployed the trust and privacy mechanism as shown in Fig. 5(c), if P2P node A is captured, the malicious

attack cannot link to the privacy information of node C. When node A spreading rumor in P2P network, the corresponding trust relations in OSN will degrade rapidly. Therefore, the consequence can be constrained in an acceptable level according to the function of the trust relations in OSN. In another case, if OSN node C is captured, the social relations are still work for node A to share files. However, the node B can be captured easily and privacy information may be disclosed. In order to enhance the security of key node, the data resources need to be encrypted [16-17] or the key nodes need more protection. Users can implement splitting target scheme themselves by register two account or running two applications in P2P network. Therefore, the splitting target scheme is less secure but more flexible with comparing to authentication intervening scheme. Table I demonstrates the result of the proposed security scheme by comparing with existing security schemes. TABLE I.

Trait Security Deployment Vulnerability Awareness requirement Applicability

ACKNOWLEDGMENT The work is supported by 863 high technology plan (Grant No. 2015AA01A707). REFERENCES [1]

[2]

[3]

[4]

[5]

[6]

PERFORMANCE SUMMARY

Coupling robustness Low Hardware Hub nodes

Authentication intervening High Software N/A

Splitting target Medium Flexible Key nodes

High

Low

Medium

Infrastructures

Access control

User

[7]

[8]

[9]

VII. CONCLUSIONS In this paper, we studied the security of interdependent networks for P2P and OSN. The security environment for P2P and OSN is examined, respectively. The security problems are derived from the cooperation and interdependence of two networks. Our analysis indicated that the main security threats are the malicious attack, especially between P2P and OSN, which also enhance the propagation of rumor. Then SICR is leveraged to model the rumor spreading in the interdependent networks. In order to enhance the security, we proposed two security schemes named authentication intervening and splitting target and their performance summaries indicate to be effective, simple, and potentially transformative way to guarantee the interdependent networks for P2P and OSN. Given the increasing trend of cooperation and dependence between P2P and OSN, the novel security threats are emerging. We believe that there is still a long way to study the security of interdependent networks.

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[11] [12]

[13] [14]

[15]

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