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Many papers have been proposed in order to increase the wireless sensor networks performance; This kind of network has limited resources, where the energy in each sensor came from a small battery that sometime is hard to be replaced or recharged. Transmission energy is the most concern part where the higher energy consumption takes place. Clustered hierarchy has been proposed in many papers; in most cases, it provides the network with better performance than other protocols. In our paper, first we discuss some of techniques, relates to this protocol, that have been proposed for energy efficiency; some of them were proposed to provide the network with more security level. Our proposal then suggests some modifications to some of these techniques to provide the network with more energy saving that should lead to high performance; also we apply our technique on an existing one that proposed to increase the security level of cluster sensor networks.
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International Journal of Network Security & Its Applications (IJNSA), Vol 1, No 2, July 2009
Clustered Hierarchy in Sensor Networks:
Performance and Security
Mohammed Abuhelaleh, Khaled Elleithy and Thabet Mismar
School of Engineering, University of Bridgeport
Bridgeport, CT 06604
{mabuhela, elleithy, tmismar} @bridgeport.edu
ABSTRACT
Many papers have been proposed in order to increase the wireless sensor networks performance; This kind of
network has limited resources, where the energy in each sensor came from a small battery that sometime is
hard to be replaced or recharged. Transmission energy is the most concern part where the higher energy
consumption takes place. Clustered hierarchy has been proposed in many papers; in most cases, it provides
the network with better performance than other protocols. In our paper, first we discuss some of techniques,
relates to this protocol, that have been proposed for energy efficiency; some of them were proposed to
provide the network with more security level. Our proposal then suggests some modifications to some of these
techniques to provide the network with more energy saving that should lead to high performance; also we
apply our technique on an existing one that proposed to increase the security level of cluster sensor networks.
KEYWORDS
LEACH (Low Energy Adaptive Clustering Hierarchy), Sensor Networks, Network Performance, Routing, Sec-
LEACH (Secure LEACH), Network security, Random KD (Key Distribution).
1. INTRODUCTION
There are many advantages of using sensor networks. They provide dynamic and wireless
communication between nodes in a network, which provides more flexible communication. At the
same time, sensor networks have some special characteristics compared to traditional networks,
which makes it harder to deal with. The most important property that affects this type of networks is
the limitation of the resources available, especially the energy.
Wireless Sensor Networks (WSNs) [2] are a special kind of Ad hoc networks that became one
of the most interesting areas for researchers. Routing techniques are the most important issue for
these networks, where resources are limited. Cluster-based organization has been proposed to
provide an efficient way to save energy during communication [3]. In this kind of organization,
nodes are organized into clusters. Cluster heads (CHs) pass messages between groups of nodes
(group for each CH) and the base station (BS), (Figure1). This organization provides some energy
saving which is the main advantage for proposing this organization. Depending on this
organization, LEACH (Low Energy Adaptive Clustering Hierarchy) [3] enhanced security, where
the CHs are rotating from node to node in the network making it harder for intruders to know the
routing elements and attack them. [4]
In this paper, we discuss some existing work of LEACH and we focus on three important
criteria; performance, security, and energy consumption. In section two, we discuss the original
work of LEACH, and then in the third section we discuss one of the most interesting modifications
proposed for LEACH to increase network performance (TCCA). In the fourth and fifth sections, we
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International Journal of Network Security & Its Applications (IJNSA), Vol 1, No 2, July 2009
discuss another two techniques that have been proposed to increase the security of LEACH (F-
LEACH and Sec-LEACH). Then, in the sixth and seventh sections, we discuss our proposal and we
explain the main modifications that we applied on LEACH and Sec-LEACH to improve network
performance and network security. In section 8, we discuss our experiment that we applied to show
the improvements that might be gained from applying our protocol compared to the existing
protocols.
2. LEACH
Low Energy Adaptive Clustering Hierarchy has been presented by [1] to balance the draining of
energy during communication between nodes in sensor networks. The BS assumed to be directly
reachable by all nodes by transmitting with high enough power. Nodes send their sensor reports to
their CHs, which then combine the reports in one aggregated report and send it to the BS. To avoid
the energy draining of limited sets of CHs, LEACH rotates CHs randomly among all sensors in the
network in order to distribute the energy consumption among all sensors. It works in rounds; in
each round, LEACH elects CHs using a distributed algorithm and then dynamically clusters the
remaining sensors around the CHs. Sensor-BS communication then uses this clustering result for
the rest of the round. (See Fig.1)
2.1. LEACH Protocol
Routing in LEACH works in rounds and each round is divided into two phases, the Setup phase
and the Steady State phase; each sensor knows when each round starts, using a synchronized clock
[1, 2].
Initially, each sensor decides if it will be a CH or not based on the desired percentage of the
CHs for the network, and the number of times the sensor has been a CH (to control the energy
consumption), this decision is made by the sensor (s) choosing a random number between zero and
one. Then it calculates the threshold for itself T(s), then it compares the random number with
resulting T(s); if the number is less than T(s), the sensor becomes a CH for the current round. T(s)
for x round with desired percentage of cluster heads P is calculated by:
T(s) =
otherwise
Gifn
P
xP
P
...................................0
........
)
1
mod(*1
(1)
Where G is a set of nodes that have not been CHs in the last 1/p round.
Setup phase includes three steps. Step1 is the advertisement step, where each sensor decides its
probability to become a CH, based on the desired percentage of CHs and its remaining energy, for
the current round; a sensor who decides to become a CH broadcasts an advertising message to other
nodes that it is ready to become a CH. Carrier sense multiple access protocol is used to avoid
collisions. Cluster joining step is the second step, where the remaining sensors pick a cluster to join
according to the highest signal received; then they send request messages to the desired CHs. Step
three starts after the CHs receive all requests from other sensors, where CHs broadcast confirmation
messages to their cluster members; these messages include the time slot schedule to be used during
the steady state phase.
The Steady State phase (the actual communication) then starts. It consists of two steps; in the
first step each node starts by sending its sensor report to its CH based on the time provided by the
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International Journal of Network Security & Its Applications (IJNSA), Vol 1, No 2, July 2009
time slot schedule. When a CH receives all the reports, it aggregates them in one report and it sends
this report to the BS (step 2). Next we show the details of each step by providing the content of each
one; for this purpose we combine the two phases in one phase with five steps.
In step one, a CH broadcasts to the rest of sensors, its ID and the Advertising message, then, in
step two, each sensor sends its ID, CH ID, and the Join Request message to its desired CH. When a
CH receives all requests, it broadcasts its ID, and the time slot schedule for sensors that includes
each member with its time slot (step three). Each sensor then sends its ID, CH ID, and the sensing
report to its CH (step four). Finally, each CH sends its ID, BS ID, and the aggregate report of its
members to the BS.
The transmission of information between sensors, and between sensors and BSs, are performed
using CSMA MAC protocol. On the other hand, they communicate using CDMA codes to reduce
the interference that may occur from communication of nearby nodes.
2.2. Energy saving in LEACH
LEACH provides many techniques for saving the total energy during network communication;
in this section we focus on the main concepts that have been applied by LEACH to save the energy.
LEACH is a self-organization adaptive protocol, and it uses randomization to evenly distribute
the energy load among the sensors in the network; this and the random way that CHs rotate around
the various sensors reduce the possible draining of the battery for each sensor.
A local data compression to compress the amount of data being sent from clusters to BS is used
to reduce the energy consumption and to enhance the system lifetime.
The time schedule that is being sent by CHs to their members, gives break time for sensors that
have not reached their time yet to be in sleeping mode, which helps them save their energy for their
scheduled time.
Finally, the nature of the way that LEACH changes CHs each round, and the way that each CH
can be elected, provides high energy saving for the whole network.
2.3. Security in LEACH
LEACH is more powerful against attacks than most other routing protocols [2, 4]. CHs in
LEACH that directly communicate with BS can be anywhere in the network and they are changing
from round to round, which makes it harder for intruders to identify the critical nodes in the
network.
On the other hand, LEACH is vulnerable to a number of security attacks [2, 4], including
spoofing, jamming, and replay attacks. Since LEACH is a cluster based protocol, it relies mainly on
the CHs for routing and data aggregation, which makes the attacks involving CHs, the most harmful
attacks.
Some kinds of attacks, such as sinkhole and selective forwarding, may occur if an intruder
manages to become a CH, which results in disrupting the work of the network.
3. TCCA
Time-Controlled Clustering Algorithm (TCCA) allows multi-hop clusters using message time-
to-live (TTL) and timestamp to control the way the clusters form. Residual energy is also
considered before a sensor volunteers to become a CH, and a numerical model is provided to
quantify its efficiency on energy usage.
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International Journal of Network Security & Its Applications (IJNSA), Vol 1, No 2, July 2009
3.1. TCCA Protocol
Similar to LEACH, TCCA’s operation is divided into rounds with two phases concluded in
each round (Setup phase and the Steady State phase). CHs are elected and the clusters are formed in
Setup phase; then the complete cycle of data collection, aggregation and transfer to the BS occurs in
the Steady State phase.
To determine the eligibility of sensor to be CH, TCCA adds some modifications to the
LEACH technique. A sensor residual energy is considered and a random number between 0 and 1
(Tmin) is generated by each sensor to determine its eligibility to become CH. If this number is less
than the variable threshold, the sensor becomes a CH for the current round. The threshold for sensor
‘s’ in round r, with desired CH percentage p, residential energy RE and maximum energy MaxE is
calculated by (2):
×
=
Gs
GsT
MaxE
RE
p
rp
p
sT
...0
min)...,
)
1
mod(1
max(
)(
(2)
G is a set of nodes that have not been CHs in the last 1/p round
When CH is elected, it advertises to other sensors to become its members; this advertisement
message contains CH ID, initial TTL, timestamp and its residual energy. Sensors receive the
message will forward it to their neighbors based on TTL value which may be based on the current
energy level of CH; at the same time they join this CH with the rest of sensors who received the
message. Once a sensor decides to join the cluster, it informs the corresponding CH by sending a
join request message that carries sensor ID, CH ID, the original timestamp from advertising
message and the remaining TTL value. The CH uses the timestamp to approximate the relative
distance of its neighbors and to learn the best setup phase time for future rounds [3].
3.2. Energy saving in TCCA
TCCA applies a new condition for electing CHs by considering the remaining energy of the
sensors. At the same time, it guarantees that every sensor will become a CH at least one time per 1/
P rounds, where P is the desired percentage of CHs. These modifications provide the network with
high energy balance by distributing the energy among all sensors.
TCCA provides optimum cluster size (K) for K-hops in order to produce high performance
similar to the performance in the one-hop network. Also it reduces the complexity of transmission
schedule generation to O (1).
TCCA uses timestamp and Time to live (TTL) tags to control the cluster formation; this leads to
gain more energy balance.
3.3. Security in TCCA
TCCA follows the main steps provided by LEACH with some modifications that do not affect
the level of security that is provided by LEACH; this means that TCCA does not have enough
protection against Spoofing, Jamming, Replay and some other kinds of attacks.
4. SEC-LEACH
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International Journal of Network Security & Its Applications (IJNSA), Vol 1, No 2, July 2009
It proposes a new modification for LEACH to increase the level of security and to protect the
network from many kinds of attacks, specially the sinkhole and selective forwarding attacks [2, 4].
Sec-LEACH proposes generating a large pool of keys and their IDs at the time the network is
deployed. Each sensor then assigned with a ring of keys taken from key pool pseudo randomly [5].
First it generates a unique ID for each sensor using a pseudo random function (PRF), then a large
enough number of keys is assigned to each sensor from the key pool; also assign each node by a
pair-wise key shared with the BS [2,5].
4.1. Sec-LEACH Protocol
When elected a CH broadcasts its advertising message, it includes the ID of the keys in its key
ring, the other sensors cluster around the nearest CH with whom they share a key [2]. The details of
Sec-LEACH protocol works as follows:
CHs are elected as in LEACH, and then these CHs broadcast their IDs and their nonce (step 1).
In step 2, other sensors computes the set of CHs keys IDs and choose the nearest CH with whom
they share a key; these sensors then send Join Request messages, protected by MAC that is
produced by the share key, and the nonce that is broadcasted by the CH, to prevent reply attacks;
the ID of the key chosen to protect the link is also sent with the to make CH knows which key to
use for verifying the MAC. To complete the setup phase, CHs send the time schedule to sensors that
choose to become their members (step3).
Step4 is the first step in Steady State phase, where sensor-to-CH communications are protected
using the same key used to protect the Join Request message. To prevent replay, a value computed
from the nonce and the reporting cycle is also included. The CH then decrypts sensor reports and
performs a data aggregation then sends it to the BS protected by the symmetric key shared with the
BS. A counter is included in the MAC value also, to provide freshness.
4.2. Energy saving in Sec-LEACH
Sec-LEACH works like the original LEACH, but here some extra bits have to be added to the
total transactions that occur during the communication in the network. As discussed in [2], these
overloads will not affect the efficiency of the original LEACH if suitable size of the key pool and
suitable number of keys assigned to each sensor are chosen.
4.3. Security in Sec-LEACH
Sec-LEACH provides more protection to the network than it is in LEACH, where it protects
against spoofing, jamming, and replay attacks. In addition, it prevents sinkhole and selective
forwarding attacks.
5. F-LEACH
F-LEACH [6] is an enhanced version of LEACH that gives protection for the network. It
suggests that each node has to have two symmetric keys: a pair-wise key shared with the BS and a
second key chain held by the BS. According to that, it suggested small modifications for LEACH.
For the setup phase, the message sent by RNs should consist of an encrypted message that contains
the ID of the node that should receive the message and the ID of the CH itself as plain text, and the
encryption (ID of CH, the counter shred by CH and the BS, and the advertisement message) using
the message authentication code (MAC) that is produced using the shared key between CH and the
BS.
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International Journal of Network Security & Its Applications (IJNSA), Vol 1, No 2, July 2009
It is already proved by [2], that Sec-LEACH provides more security and performance than in F-
LEACH, so we will not go through that technique in detail.
6. MODIFIED LEACH
To improve LEACH we insinuate Modified LEACH (Mod-LEACH). Mod-LEACH works in
two rounds: a Full transmission round and a half transmission one.
Each sensor checks its ability to become a CH depending on the desired percentage of CHs,
current round, and the remaining energy; we used the same formula used by TCCA to calculate the
threshold.
The sensors that are able to become a CH (ready sensors) for the current round start listening
for any query that might be sent by other sensors; the other sensors start broadcasting their reports
to their neighbors, the packets contain some other tags to determine the status of the packets; any
ready sensor that receives the report saves it temporarily and sends a confirmation/request to the
related sensor confirming that it is ready to send its report and providing its ability status to become
a CH for next round. Sensors who receive the confirmation, reply back to the CH with another
confirmation and save the CH id to use it for the next round (if the status of the CH shows that it is
able to be a CH for two rounds). CHs will then collect all the reports that have been confirmed in
one compressed report and forwards it to the BS (This is considered as a full transmission round).
For the next round, the sensors with no CHs will repeat the same scenario, and the sensors with
CHs will send the report only to their CHs; when the old CHs receive the reports, it will aggregate
them in one report and forward it to the BS (this considered as a half transmission report).
Next we will explain in details the complete protocol.
6.1. Mod-LEACH Protocol
The operation of the Mod-LEACH occurs in rounds, and rounds are classified into two kinds,
the full transmission round and the half transmission round. The main idea here is to skip the setup
phase that is proposed by all other discussed protocols.
At the beginning of each round, CHs elect themselves. In order to determine the eligibility of a
sensor to be a CH, each sensor (S) generates a random number between 0 and 1; then this number is
compared to a sensor variable threshold value T(S); if the value of the threshold is greater than the
random number, the sensor becomes a CH for the current round (R). The Threshold value can be
calculated using the same formula that is used by TCCA [3]; first it calculates the threshold for two
rounds as follows:
)3...(
......,..................................................0
min)...,...
2*
Re
)
1
mod(1
max(
)(
×
=
otherwise
GifsT
MaxEng
mEng
P
RP
P
asT
If formula (3) is approved, then it is ready to become a CH for two rounds. If formula (3) is not
approved, the sensor will calculate formula (4) to see if it is able to become a CH for only one
round.
)4...(
......,..................................................0
min)...,...
Re
)
1
mod(1
max(
)(
×
=
otherwise
GifsT
MaxEng
mEng
P
RP
P
asT
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International Journal of Network Security & Its Applications (IJNSA), Vol 1, No 2, July 2009
Where P is the desired percentage of CHs, Tmin is a minimum threshold (to avoid the possibility of
remaining energy shortage), and G is the set of sensors that have not became CHs in 1/P round,
MaxEng is the maximum energy that the sensor could have, RemEng is the sensor remaining
energy.
Each elected CH starts listening to the network; other sensors start broadcasting their reports to
their neighbors (using Carrier sense multiple access protocol for transmission to avoid collisions);
this message consists of Sensor ID, report, Requesting type tag (RT: 0 for request, 1 for approves),
Time to live (TTL: set to 1, broadcast to only direct neighbors), packet request status tag (PR: 0 for
the first packet, 1 for the second packet). When ready sensors (CHs) receive the messages, it saves
each report with the node id temporarily in its memory, and then it sends requests with confirmation
to those sensors indicating that it is ready to become their CH for the current round, when formula3
applies, it also indicates that it is also ready to be their CH for the next round; the message contains:
CH id, pairs of Sensor id with its time (to prevent collisions and provide less delay), TTL (set to 1),
RT (set to 1), PR (set to 0) and the ability tag (AT: 0 for one round ability, and 1 for two rounds
ability). Sensors receive the message from CHs; if they receive more than one request then they will
choose the one with the ability to become CH for two rounds, AT=1 (here it will save the CH id to
use it in the next round); if they receive many requests with the same values, then they pick the CH
randomly; Sensors then reply to CHs with confirmation; the message contains: Sensor id, CH id,
and an Acknowledgment tag (ACK: set to 1). When a CH receives the confirmations it combines all
collected reports in one compressed report and forwards it to the BS; the message contains: CH id,
BS id and the aggregation report.
In the next round, sensors check first if they are group members of a CH with an ability to
handle two rounds, if they are, then they use it for the current round (half transmission round is
applied); the sensor sends its report to its CH; the message contains: Sensor id, CH id, PR (set to 1),
TTL (set to 1), PR (set to 1). CH receives the reports, aggregate then in one report, and then send
them to the BS, the message contains: Ch id, BS id, and the aggregation report; then the CH will
send acknowledgments to its members and remove them from its memory; the acknowledgment
message contains: Ch id, Sensor id, and ACK (set to 1); sensors who receive the acknowledgment
then remove CH info from their memories.
In the case that the sensor does not have a CH from the previous round, it will repeat the first
scenario for full round transmission.
6.2. Energy saving in Mod-LEACH
Mod-LEACH applies the same condition that has been applied by TCCA for electing CHs by
considering the remaining energy of the sensors. At the same time, it guarantees that every sensor
will become a CH at least one time per 1/P rounds, where P is the desired percentage of CHs. These
modifications provide the network with high energy balance by distributing the energy among all
sensors.
Mod-LEACH provides enhanced energy saving by dealing with double round technique, where
it saves almost half of the energy used in one regular round; for the full transmission round, it will
consume more energy than LEACH and TCCA, but it covers that gab in the next round, and even
saves more energy than other protocols may save.
Mod-LEACH uses Time to live (TTL) tags to control the cluster formation, where the
broadcasting occurs only on the direct neighbors; this leads to a more energy balanced network.
6.3. Security in Mod-LEACH
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International Journal of Network Security & Its Applications (IJNSA), Vol 1, No 2, July 2009
Mod-LEACH provides the same level of security that has been provided by LEACH and
TCCA, where it didn’t affect the main idea of these protocols which is the dynamic rotation of CHs
around the network.
7. MODIFIED SEC-LEACH
Here we apply the same technique that we proposed for Mod-LEACH, in a way that deals with
the security proposal that been suggested by Sec-LEACH.
After generating the key pool and assigning the groups of keys for each node, in addition to a
pair-wise key for each of them, we can start our protocol.
The sensors start sending their reports to their direct neighbors; the sensors that are ready to
become CHs, receive the reports, store them temporarily and inform the desired sensors with their
ability to send their reports; the message will also include the duration that the CH may handle the
cluster (one or two rounds). The sensors that received the confirmation, replies to the nearest
neighbors (higher signals) with higher ability (two rounds) with acknowledgment and a permission
to send; the CHs then will combine the reports in one compressed report and forward it to the BS; if
the sensor connects with a CH that can handle two consecutive rounds, then it will implicitly
consider it as its CH, so in the next round it will only send its report to its CH and then the CH will
combine the sensor report with other reports like before and send it to the BS; then the CH will send
an acknowledgment to its members that the reports have been sent.
All the steps pass through the encryption technique provided by Sec-LEACH using the random
key distribution.
7.1. Mod-Sec-LEACH Protocol
The operation of the Mod-Sec-LEACH occurs in rounds, and rounds are classified into two
kinds, the full transmission round and the half transmission round. The main idea here is to skip the
setup phase that is proposed by all other discussed protocols.
Prior to network deployment, each sensor is assigned a group of keys randomly from big key
pool provided by the BS. A pseudo random function is used to produce the keys IDs; These IDs
then, map to their corresponding values in the key pool. Also each sensor assigned by a pair-wise
key sharing it with the BS for secure direct communication.
At the beginning of each round, CHs elect themselves. In order to determine the eligibility of a
sensor to be a CH, each sensor (S) generates a random number between 0 and 1; then this number is
compared to a sensor variable threshold value T(S); if the value of the threshold is greater than the
random number, the sensor becomes a CH for the current round (R). The Threshold value can be
calculated using the same formula that is used by TCCA; first it calculates the threshold for two
rounds as in formula (3).
If formula (3) is approved, then it is ready to become a CH for two rounds; if not, then sensor
checks its ability to become CH for only one round, by applying formula (4).
Each elected CH starts listening to the network; other sensors start broadcasting their reports to
their neighbors (using carrier sense multiple access protocol for transmission to avoid collisions);
this message consists of Sensor ID, the ID of the common key that is picked from the sensor keys
ring (CK), Requesting type tag (RT: 0 for request, 1 for approves), Time to live (TTL: set to 1,
broadcast only to direct neighbors), packet request status tag (PR: 0 for the first packet, 1 for the
second packet), and the encryption of sensor id and the report, all encrypted using the Message
Authentication Code (MAC) that was produced using CK. When ready sensors (CHs) receive the
messages, it checks if it shares the same key/s with those who sent the messages; if it is, then it
saves each report with the node id temporarily in its memory, and then it sends requests with
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International Journal of Network Security & Its Applications (IJNSA), Vol 1, No 2, July 2009
confirmation to those sensors indicating that it is ready to become their CH for the current round,
when formula5 applies, it also indicates that it is also ready to be their CH for the next round; the
message contains: CH id, pairs of Sensor id with its time (to prevent collisions and provide less
delay), TTL (set to 1), RT (set to 1), PR (set to 0) and the ability tag (AT: 0 for one round ability,
and 1 for two rounds ability). Sensors receive the message from CHs; if they receive more than one
request then they will choose the one with the ability to become CH for two rounds, AT=1 (here it
will save the CH id to use it in the next round); if they receive many requests with the same values,
then they pick the CH randomly; Sensors then reply to CHs with confirmation; the message
contains: Sensor id, CH id, CK, an Acknowledgment tag (ACK: set to 1), and the encryption of
(Sensor id, CH id, CK, and ACK), encrypted using the MAC produced by sensors CKs. When a CH
receives the confirmations it decrypt and combines all the reports that it has in one compressed
report and forwards it to the BS; the message contains: CH id, BS id, the aggregation report, and the
encryption of (CH id, BS id, and the aggregation report) encrypted by the MAC produced by CH
CK.
In the next round, sensors check first if they are group members of a CH with an ability to
handle two rounds, if they are, then they use it for the current round (half transmission round is
applied); the sensor sends its report to its CH; the message contains: Sensor id, CH id, CK, PR (set
to 1), TTL (set to 1), PR (set to 1), and the encryption of (Sensor id, CH id, CK, PR, TTL, and PR),
all encrypted using sensor CK . CH receives the reports, decrypt and aggregate them then in one
report, and then send them to the BS, the message contains: CH id, BS id, CK, the aggregation
report, and the encryption of (CH id, BS id, CK, and the aggregation report) encrypted by the MAC
produced from CH CK; then the CH will send acknowledgments to its members and remove them
from its memory; the acknowledgment message contains: CH id, Sensor id, CK, ACK (set to 1),
and the encryption of (CH id, Sensor id, CK, and ACK) encrypted using the MAC produced from
CH CK; sensors that receive the acknowledgment remove CH info from their memories.
In the case that the sensor does not have a CH from the previous round, it will repeat the first
scenario for the full round transmission Like in LEACH.
8. EXPERIMENTATION AND ANALYSIS
In this section, we discuss the numerical experimentation; here we describe the chosen
parameters groups for each protocol, following the same scenario. The experiment is applied on
LEACH, TCCA, Sec-LEACH, Mod-LEACH, and Mod-Sec-LEACH protocols; we applied them on
three different network sizes (100, 1000, and 10000 sensors); for each size, 1000 rounds were
processed with the following initial values of main parameters:
- The desired percentage of CHs (P) is set to 0.05.
- Each sensor starts with 0.5 j energy.
- The amplifier energy is assumed to be 100 pj.
- The electronic energy is assumed to be 50 nj.
- Each sensor data range is set to 30m.
- The message size of a sensor data is set to 50 bits.
- Each node has 2000-bit data packet to send to the BS.
8.1. Energy Saving
LEACH provides many techniques to save energy during network communication; where it is a
self-organization, adaptive protocol and it uses randomization to evenly distribute the energy load
among the sensors in the network, in addition to the random way that CHs rotate around the various
sensors which is reducing the possible draining of the battery for each sensor. Also, performing a
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International Journal of Network Security & Its Applications (IJNSA), Vol 1, No 2, July 2009
local data compression to compress the amount of data being sent from clusters to BS reduces the
energy consumption and enhances the system lifetime. These factors, in addition to the way that
CHs change every cycle provide LEACH with High energy saving. Mod-LEACH applies the same
factors to Sensor networks which provide it with similar energy saving to the LEACH at this point.
TCCA adds additional factors to save energy; it uses Time to live (TTL) tag to control the
cluster formation, which leads to gain more energy balance. It also uses the new condition provided
by TCCA to elect CHs each round, which results in more energy control. [3] Shows that TCCA
works almost three times better than LEACH in energy saving. Mod-LEACH and Mod-Sec-
LEACH applied TCCA factors, which means that it works three times better than LEACH in energy
saving. Now by applying the new idea that we discussed before, we can notice that Mod-LEACH
and Mod-Sec-LEACH provide the network with almost four times more energy saving than what is
provided by LEACH, and almost double of that in TCCA.
Our experiment shows that the variation of energy consumption is very small when network
size is small (i.e. 100 sensors), but it varies more if we increase the network size. Fig.3 shows that,
for network size of 10,000 sensors, total energy consumption is minimum in Mod-LEACH with
almost 0.3X1012 nj, then Mod-Sec-LEACH comes with energy consumption of almost 0.7X1012 nj,
then TCCA comes with energy consumption of almost 1.3X1012 nj at third place, at fourth place
LEACH comes with 3.3X1012 nj, and finally Sec-LEACH comes with 4.1X1012 nj. The variation
comes from the nature of how Mod-LEACH and Mod-Sec-LEACH works; using TTL, in addition
to continuous checking of residual energy of each sensor, gives Mod-LEACH and TCCA protocols
more energy balance for large network size; double round technique provides Mod-LEACH and
Mod-Sec-LEACH with more energy saving.
8.2. Data Overload
TCCA works with multi-hops clusters; this reduces the number of clusters, which reduces
the total transactions required in network communications; this leads to highly reduce data overload
compared with LEACH. Mod-LEACH and Mod-Sec-LEACH have two different round types; in
the full transmission round it will produce more data overload than that produced by TCCA,
60
Fig.3. Total energy consumption occur in LEACH, TCCA,
Sec-LEACH, Mod-LEACH and Mod-Sec-LEACH after
1000 rounds, for different network sizes (100, 1000,
10000).
International Journal of Network Security & Its Applications (IJNSA), Vol 1, No 2, July 2009
LEACH, and Sec-LEACH, but by applying the half transmission technique on the next round, we
balance the increase in the data in the previous round and we provide less total data overload than
that provided in double rounds with LEACH, TCCA, and Sec-LEACH.
Our experiment shows that, for a large network size (i.e. 10000 sensors); the total data
overload is minimized using Mod-LEACH. Fig.4 shows that with Mod-LEACH data overload
reaches almost 0.2X1010 bits; in Mod-Sec-LEACH, it reaches 0.4X1010 bits where in TCCA it
reaches 2.2X1010 bits,; in LEACH it reaches 9.3X1010,, and in Sec-LEACH, it reaches 12X1010 bits;
this shows that Sec-LEACH produces data overload almost 12 times than Mod-LEACH and Mod-
Sec-LEACH; LEACH produces more data overload, almost nine times more than the data overload
produced by Mod-LEACH and Mod-Sec-LEACH. Moreover, TCCA produces more data overload,
almost five times than data overload produced by Mod-LEACH and Mod-Sec-LEACH.
8.3. Performance
According to the energy saving analysis, we can figure out that the number of Dead Nodes that
may appear in LEACH and Sec-LEACH will be much higher than the number of dead nodes in
Mod-LEACH and Mod-Sec-LEACH, where the number of Dead Nodes depends on the energy
consumption by the network (Fig.5).
61
Fig.4. Total data overload in LEACH, TCCA, Sec-
LEACH, Mod-LEACH, and Mod-Sec-LEACH after
1000 rounds for different network sizes (100, 1000,
10000).
Fig.5. Dead nodes occur in LEACH, TCCA, Sec-
LEACH, Mod-LEACH, and Mod-Sec-LEACH
after 1000 rounds, for different network sizes (100,
1000, 10000).
International Journal of Network Security & Its Applications (IJNSA), Vol 1, No 2, July 2009
9. CONCLUSIONS
The results shows that our proposal should provide wireless sensor networks with high
performance; also it shows that our proposal is flexible and can be applied to other techniques that
are related to the clustered hierarchy without affecting the main purpose of the original technique,
more specifically is the security level that can be achieved using that protocol; at the same time it
provides it with better performance.
REFERENCES
[1] W. R. Heinzelman, A. Chandrakasan, and H. Balakrishnan. Energy-efficient communication
protocol for wireless microsensor networks. In IEEE Hawaii Int. Conf. on System Sciences, pages 4–
7, January 2000.
[2] Leonardo B. Oliveira, Hao C. Wong, M. Bern, Ricardo Dahab, A. A. F. Loureiro. SecLEACH - A
Random Key Distribution Solution for Securing Clustered Sensor Networks. Fifth IEEE
International Symposium on Network Computing and Applications (NCA'06)
[3] S. Selvakennedy, and S. Sinnappan. A Configurable Time-Controlled Clustering Algorithm for
Wireless Networks. 2005 11th International Conference on Parallel and Distributed Systems
(ICPADS’05).
[4] Chris Karlof, Naveen Sastry, and David Wagner. TinySec: A Link Layer Security Architecture for
Wireless Sensor Networks. 2004 Conference on Embedded Networked Sensor Systems Proceedings
of the 2nd international conference on Embedded networked sensor systems.
[5] Sencun Zhu, Shouhuai Xu, Sanjeev Setia, and Sushil Jajodia. Establishing Pairwise Keys for Secure
Communication in Ad Hoc Networks: A Probabilistic Approach. Proceedings of the 11th IEEE
International Conference on Network Prot1ocols (ICNP’03)
Authors
Dr. Khaled Elleithy received the B.Sc. degree in computer science and automatic control from
Alexandria University in 1983, the MS Degree in computer networks from the same university in
1986, and the MS and Ph.D. degrees in computer science from The Center for Advanced Computer
Studies at the University of Louisiana at Lafayette in 1988 and 1990, respectively. From 1983 to
1986, he was with the Computer Science Department, Alexandria University, Egypt, as a lecturer.
From September 1990 to May 1995 he worked as an assistant professor at the Department of
Computer Engineering, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia.
From May 1995 to December 2000, he has worked as an Associate Professor in the same
department. In January 2000, Dr. Elleithy has joined the Department of Computer Science and
Engineering in University of Bridgeport as an associate professor. In May 2003 Dr. Elleithy was
promoted to full professor. In March 2006, Professor Elleithy was appointed Associate Dean for
Graduate Programs in the School of Engineering at the University of Bridgeport.
Mohammed Abuhelaleh is a full-time Ph.D. student of Computer Science and Engineering at the
University of Bridgeport. He worked as a lecturer for Alhusein Bin Talal Universtity; He thought
some computer science courses, in addition to college courses, like Data Structure, C++, and
Computer Skills for three years. He has master degree Computer Science from University of
Bridgeport, and graduated with a GPA of 3.48. Mohammed now is at the end Of fifth semester of
PHD program. Mohammed worked as Graduate Assistant for many times under Prof. Elleithy.
Thabet Mismar is a full-time M.Sc. student of Electrical Engineering at the University of Bridgeport.
He has B.Sc. degree of Electrical Engineering from the University of Jordan. Thabet is now in the last
semester of the M.Sc. program and he worked as a graduate assistant for Prof. Elleithy at the dean of
engineering and technology office at the University of Bridgeport.
62
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Conference Paper
Full-text available
Clustered sensor networks have been shown to increase system throughput, decrease system delay, and save energy. While those with rotating cluster heads, such as LEACH, have also advantages in terms of security, the dynamic na- ture of their communication makes most existing security solutions inadequate for them. In this paper, we show how random key predistribution, widely studied in the context of flat networks, can be used to secure communication in hier- archical (cluster-based) protocols such as LEACH. To our knowledge, it is the first work that investigates random key predistribution as applied to hierarchical WSNs.
Conference Paper
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Future large-scale sensor networks may comprise thousands of wirelessly connected sensor nodes that could provide an unimaginable opportunity to interact with physical phenomena in real time. These nodes are typically highly resource-constrained. Since the communication task is a significant power consumer, there are various attempts to introduce energy-awareness at different levels within the communication stack. Clustering is one such attempt to control energy dissipation for sensor data routing. Here, we propose the time-controlled clustering algorithm to realise a network-wide energy reduction by the rotation of clusterhead role, and the consideration of residual energy in its election. A realistic energy model is derived to accurately quantify the network's energy consumption using the proposed clustering algorithm
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Wireless distributed microsensor systems will enable the reliable monitoring of a variety of environments for both civil and military applications. In this paper, we look at communication protocols, which can have significant impact on the overall energy dissipation of these networks. Based on our findings that the conventional protocols of direct transmission, minimum-transmission-energy, multi-hop routing, and static clustering may not be optimal for sensor networks, we propose LEACH (Low-Energy Adaptive Clustering Hierarchy), a clustering-based protocol that utilizes randomized rotation of local cluster based station (cluster-heads) to evenly distribute the energy load among the sensors in the network. LEACH uses localized coordination to enable scalability and robustness for dynamic networks, and incorporates data fusion into the routing protocol to reduce the amount of information that must be transmitted to the base station. Simulations show the LEACH can achieve as much as a factor of 8 reduction in energy dissipation compared with conventional outing protocols. In addition, LEACH is able to distribute energy dissipation evenly throughout the sensors, doubling the useful system lifetime for the networks we simulated.
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We introduce TinySec, the first fully-implemented link layer security architecture for wireless sensor networks. In our design, we leverage recent lessons learned from design vulnerabilities in security protocols for other wireless networks such as 802.11b and GSM. Conventional security protocols tend to be conservative in their security guarantees, typically adding 16--32 bytes of overhead. With small memories, weak processors, limited energy, and 30 byte packets, sensor networks cannot afford this luxury. TinySec addresses these extreme resource constraints with careful design; we explore the tradeoffs among different cryptographic primitives and use the inherent sensor network limitations to our advantage when choosing parameters to find a sweet spot for security, packet overhead, and resource requirements. TinySec is portable to a variety of hardware and radio platforms. Our experimental results on a 36 node distributed sensor network application clearly demonstrate that software based link layer protocols are feasible and efficient, adding less than 10% energy, latency, and bandwidth overhead.
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A prerequisite for a secure communication between two nodes in an ad hoc network is that the nodes share a key to bootstrap their trust relationship. In this paper, we present a scalable and distributed protocol that enables two nodes to establish a pairwise shared key on the fly, without requiring the use of any on-line key distribution center. The design of our protocol is based on a novel combination of two techniques - probabilistic key sharing and threshold secret sharing. Our protocol is scalable since every node only needs to possess a small number of keys, independent of the network size, and it is computationally efficient because it only relies on symmetric key cryptography based operations. We show that a pairwise key established between two nodes using our protocol is secure against a collusion attack by up to a certain number of compromised nodes. We also show through a set of simulations that our protocol can be parameterized to meet the desired levels of performance, security and storage for the application under consideration.
Total energy consumption occur in LEACH, TCCA, Sec-LEACH, Mod-LEACH and Mod-Sec-LEACH after 1000 rounds, for different network sizes (100
  • Fig
Fig.3. Total energy consumption occur in LEACH, TCCA, Sec-LEACH, Mod-LEACH and Mod-Sec-LEACH after 1000 rounds, for different network sizes (100, 1000, 10000).
Advanced Computer Studies at the University of Louisiana at Lafayette in 1988 and 1990, respectively. From 1983 to 1986, he was with the Computer Science Department
  • Dr
Dr. Khaled Elleithy received the B.Sc. degree in computer science and automatic control from Alexandria University in 1983, the MS Degree in computer networks from the same university in 1986, and the MS and Ph.D. degrees in computer science from The Center for Advanced Computer Studies at the University of Louisiana at Lafayette in 1988 and 1990, respectively. From 1983 to 1986, he was with the Computer Science Department, Alexandria University, Egypt, as a lecturer. From September 1990 to May 1995 he worked as an assistant professor at the Department of Computer Engineering, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia. From May 1995 to December 2000, he has worked as an Associate Professor in the same department. In January 2000, Dr. Elleithy has joined the Department of Computer Science and Engineering in University of Bridgeport as an associate professor. In May 2003 Dr. Elleithy was promoted to full professor. In March 2006, Professor Elleithy was appointed Associate Dean for Graduate Programs in the School of Engineering at the University of Bridgeport.