secure wireless network connectivity in the presence of eavesdroppers

International Journal of Emerging Technologies and Engineering (IJETE) Volume 1 Issue 10, November 2014, ISSN 2348 – 8050

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Secure Wireless Network Connectivity In The Presence of Eavesdroppers

S.Suganya1, T.Parthiban

2

1.M.E Student, Kongunadu College of Engineering and Technology, Trichy

2. Assistant Professors/CSE DEPT, Kongunadu College of Engineering and Technology, Trichy

ABSTRACT In wireless ad hoc networks the sender and receiver

should sharing the message with secure and timely

manner. Each nodes communicate through an

intermediate node which are moving over the network.

The nature of an intermediate or relay node should

produce the throughput performance on entire network.

Relay transmission can enhance coverage and

Throughput. In this paper, consider the transmission of a

confidential message from a source to a destination in a

decentralized wireless network in the presence of

randomly distributed eavesdroppers. The source–

destination pair off can be potentially assisted by

randomly dispersed relays. For an arbitrary relay,

develop exact expressions of secure link probability for

both colluding and noncolluding eavesdroppers. To

obtain lower bound expressions on the secure connection

probability, which are correct when the eavesdropper

density is small. Using these lower bound terminology,

propose a relay selection strategy to improve the secure

connection probability. By analytically compare the

secure connection probability for direct transmission and

relay transmission, to address the important problem of

whether or not to relay and discuss the condition for

relay transmission in terms of the relay density and

source–destination space. These analytical results are

accurate in the small eavesdropper density regime. There

is no link failure between nodes because each node

having static velocity. If data loss is occurred any node

that node should retransmit the data to neighbor without

the involvement of source node. It will save the energy

of relay node. A trust based security protocol based on a

MAC-layer approach which attains confidentiality and

authentication of packets in both routing and link layers

of MANETs.

Key words: Secure connection probability, Colluding

eavesdropper, Non colluding eavesdropper, Direct

transmission, Relay transmission, Wireless adhoc

networks.

1. INTRODUCTION The research on wireless ad hoc networks has

experienced a rapid growth over the last few years.

Unique properties of adhoc networks, such as operation

without preexisting transportation, quick deployment,

and self-configuration, make them suitable for

communication in tactical operations, search and rescue

missions, and home networking. While the majority

studies in this region have concentrated on the design of

routing protocols, medium access manage protocols, and

security issues, look into the efficiency of energy

consumption in wireless ad hoc networks in this work.

Due to their portability and quick deployment in

potentially harsh scenarios, nodes in ad hoc networks are

usually powered by batteries with finite capacity.

FIGURE 1: Wireless Adhoc networks

It is always desirable to extend the lifetime of ad hoc

network nodes without sacrificing their functionality.

Thus, the study of energy-efficient mechanisms is of

importance. In wireless ad hoc networks, energy

consumption at each node is mainly due to system

operation, data processing, and wireless transmission

and response. While there are studies on rising battery

capacity and reducing energy consumption of system

operation and data processing, energy consumption

economy of radio transceivers has not received as much

attention.

FIGURE 1: A Network with multiple terminals

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The direct fading link connecting the legitimate users

Alice and Bob, the fading channels between Alice and

relays and between Bob and relays can also serve as

additional random sources for key generation.

Information security of wireless communications has

taken on an increasingly important role as these

networks continue to flourish worldwide.

Communications over wireless networks are particularly

vulnerable to eavesdropping attacks due to the broadcast

nature of the wireless medium. To protect confidential

message transmission, physical layer security has been

developed as a promising mechanism which provides the

protection at the physical layer by exploiting the random

and noisy nature of the wireless propagation channels. A

key feature of physical layer security is that the level of

security provided strongly depends on the amount of

information that the legitimate users know about the

eavesdroppers. In particular, perfect secrecy may not be

always achievable if the channel state information (CSI)

of the eavesdropper is not perfectly known. In this paper,

we try to address the question of whether or not to use

relay transmission in wireless ad hoc networks from a

secure connectivity perspective.

Firstly, assuming that a relay at an arbitrary location is

already selected, derive the exact expression of secure

connection probability for relay transmission. Then, a

lower bound on the secure connection probability is

provided in order to further study the optimal relay

selection strategy. Derive the secure connection

probability for direct transmission from the source to the

destination. Having the secrecy performance of both

relay transmission and direct transmission provide an

respond to whether or not to use relay transmission. In

particular, provide an analytical expression on the

condition for relay transmission in terms of the relay

density and the distance between the source and

destination, for a given target secure connection

probability. The analytical results are very accurate in

the small eavesdropper density regime.

2. RELATED WORKS In[1] P. C. Pinto, J. Barros, and M. Z. Win, In some

applications, this assumption may underestimate the

eavesdroppers’ power: they can collude, i.e., share their

channel outputs , and render the attack more effective.

Hence, combating colluding eavesdroppers, particularly

in wireless networks, has been a significant challenge.

To the best of our knowledge, all previous works

modeled k colluding eavesdroppers as one eavesdropper

with k antennas; we term these perfect colluding

eavesdroppers. Using the corresponding Single-Input

Multiple Output (SIMO) Gaussian wiretap channel, the

information leak is determined by the aggregate Signal

to Noise Ratio (SNR) of all eavesdroppers; compared to

the maximum SNR in the non-colluding case. This

assumption significantly overestimates the

eavesdropping capability, forcing a legitimate user to

increase its power linearly with the number of

eavesdroppers to achieve a positive secure rate.

However, collusion necessitates communication

resources and power utilization. This, in fact, restricts

the collusion channel capacity and thus improves the

achievable secure rate by the legitimate user.

In [6] O. O. Koyluoglu, C. E. Koksal, and H. El Gamal,,

it has been shown that under the RaF strategy, securing

each individual hop is sufficient for securing the end-to-

end transmission, so the message is secured if the two

hops are both secured.

In [8] A. D. Wyner, the author to protect confidential

message transmission, physical layer security has been

developed as a promising mechanism which provides the

protection at the physical layer by exploiting the random

and noisy nature of the wireless propagation channels. A

key feature of physical layer security is that the level of

security provided strongly depends on the amount of

information that the legitimate users know about the

eavesdroppers. In particular, perfect secrecy may not be

always achievable if the channel state information (CSI)

of the eavesdropper is not perfectly known.

In [10] J. Wang, P. Huang, and X. Wang,.the author

defined the cross layer resource allocation problem in

the multi-user downlink environment for both having

instantaneous and partial eavesdropping channel

information scenario. The problem is first formulated in

a new security structure. Then, the control scheme is

considered to maximize the average admission rate of

the information, incorporate delay, power, and secrecy

as constraint, for both non-colluding and colluding

eavesdropping cases in each scenario.

In [4] M. Haenggi, J. G. Andrews, F. Baccelli, O.

Dousse, and M. Franceschetti In this case, different

techniques based on stochastic geometry and the theory

of random geometric graphs including point procedure

theory, percolation theory, and probabilistic

combinatorics – have led to results on the connectivity,

the capacity, the outage probability, and other

fundamental limits of wireless networks.

3. DESCRIPTION OF THE SCHEME 3.1 SYSTEM MODEL

A relay network consisting of one source , several

relays, one destination, and several eavesdroppers. All

the nodes are equipped with one antenna. The source has

the instantaneous CSI of the links from the source to the

relays and from the source to the destination, and the

relays have the instantaneous CSI of the links from the



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relays to the destination. Assume the source and the

relays do not have the instantaneous CSI of the links

from the source to the eavesdroppers and from the relays

to the eavesdroppers, respectively. In this paper, the

source performs relay selection and decides whether a

relay is needed.

FIGURE 1: System model

3.2 RELAY TRANSMISSION AND DIRECT

TRANSMISSION

The communication protocol is a hybrid mode that

allows adaptive switching between direct transmission

and relay transmission. In this paper, however, consider

a switching criterion with priority on the use of a direct

transmission. Then, the relay transmission is only used

when the direct path does not satisfy the target security

requirement. For relay transmission, we use RaF

strategy. The communication is divided into two slots. In

the first time slot, the source sends data to the relays. In

the second time slot, only the selected relay sends data to

the destination.

3.3 PERFORMANCE ANALYSIS OF

EAVASDROPPER

There are two types of eavesdroppers depending on

whether the eavesdroppers join the received information:

colluding eavesdroppers and non-colluding

eavesdroppers. The colluding eavesdroppers case is the

worst situation from the secure message viewpoint. It

means that all the eavesdroppers can exchange and

combine the received information to decode the secret

message.

On the other hand, the non colluding eavesdroppers case

means that the eavesdroppers are not allowed to collude,

and secure performance is determined with the strongest

received signal from the transmitter.

In this part, study the secure connection probability for

colluding eavesdroppers, and obtain the exact

expressions of secure connection probability for the

direct transmission and relay transmission assuming an

arbitrary relay, respectively. Then the lower bound for

colluding eavesdroppers is obtained, and the lower

bound gives accurate approximation of the exact

performance when the eavesdropper density is small.

Using the lower bound, to find that the optimum relay is

the nearest one to the midpoint between the source and

destination, and get the lower bound expression for relay

selection.

FIGURE 4: Out degree of a node. The node at the origin

can transmit messages with information-theoretic

security to NOUT = 3 nodes.

4. EXPERIMENT RESULTS A relay network consisting of one source (S), several

relays (Rl , l = 1, 2, . . .), one destination (D), and several

eavesdroppers (E j , j = 1, 2, . . .). All the nodes are

equiped with one antenna. The distance between the

source and destination is equal to dSD. The distributions

of relays and eavesdroppers are homogenous PPPs ΦR

and ΦE with density λR and λE, respectively. In this

system, all the transmitters transmit with the same

power. Then can obtain the instantaneous signal-to-noise

ratio (SNR) at the relays, destination, and eavesdroppers.

The direct transmission match the simulation results

perfectly for two strategies. The lower bounds of secure

connection probability for relay transmission for both

the two strategies are very close to the simulation results,

when λE is low, and the gap between them becomes

larger with λE increasing. Secondly, the secure

connection probability for non-colluding eavesdroppers

is better than that of colluding eavesdroppers. Thirdly, it

is shown that the secure connection probability for relay

transmission depends on the relay density. When λR is

low, the secure connection probability for relay

transmission is worse.

According to RaF means that the source and relay use

independent randomization signal in each hop. The

communication is divided into two slots. In the first time

slot, the source sends data to the relays. In the second

time slot, only the selected relay sends data to the

destination. The RaF strategy, securing each individual

hop is sufficient for securing the end-to-end

transmission, so the message is secured if the two hops

are both secured.



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In this section obtain the exact expressions of secure

connection probability for the direct transmission and

relay transmission assuming an arbitrary relay,

respectively.

Then analyze the lower bound for non-colluding

eavesdroppers and find that the lower bound is close to

the exact performance when the eavesdropper density is

small. Using the same optimum relay selection strategy

with colluding eavesdroppers, obtain the lower bound

expressions for relay selection.

Improve the secure connection probability through a

relay selection strategy. The secure performance is

determined with the strongest received signal from the

transmitter.

Comparing the direct transmission with the relay

transmission, we find that whether or not to relay

transmission depends on the relay density and the

distance between the source and destination for a given

target secure connection probability. The results

obtained from this study provide useful design insights

for relay networks with security constraints.

5. CONCLUSION In this paper, analyzed the secure connection probability

of direct transmission and relay transmission for

colluding eavesdroppers and non-colluding

eavesdroppers strategies, where the distributions of

relays and eavesdroppers follow homogenous PPPs. The

lower bound expressions of secure connection

probability using RaF for colluding eavesdroppers and

non-colluding eavesdroppers strategies are obtained, and

it shows that the lower bound gives accurate

approximation of the exact performance in the small

eavesdropper density regime. Comparing the direct

transmission with the relay transmission, discover that

whether or not to relay transmission depends on the

relay density and the distance between the source and

destination for a given target secure connection

probability. The results obtain from this study provide

useful design insights for relay networks with security

constraints. A trust based packet forwarding scheme for

detecting and isolating the malicious nodes using the

routing layer information. It use trust values to favor

packet forwarding by maintaining a trust counter for

each node. The proposed MAC-layer security protocol

achieves High packet delivery ratio while attain short

delay, high speed and overhead.

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DirectLink(Monte Carlo simulation colluding)

RelayCooperationλR=10−4(Monte Carlo simulation colluding)

RelayCooperationλR=10−4(Monte Carlo simulation colluding)

Direct link(Monte Carlo simulation noncolluding)

RelayCooperationλR=10−3(Monte Carlo simulation noncolluding)

RelayCooperationλR=10−4(Monte Carlo simulation noncolluding)



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