This document is a seminar report by Swapnil S. Jagtap on methods for secure and efficient data transmission in cluster-based wireless sensor networks (WSNs). It proposes two protocols, SET-IBS and SET-IBOOS, leveraging digital signature schemes to enhance security, with detailed analyses on their effectiveness concerning energy consumption and security overhead. The report also includes an overview of WSN architectures, components, and various routing techniques while addressing the significance of secure data transmission in critical applications.

1. Cluster-based Wireless Sensor Network
(WSN) Methods for Secure and Efficient
Data Transmission
A SEMINAR-I REPORT
SUBMITTED TO
SAVITRIBAI PHULE PUNE UNIVERSITY, PUNE
FOR THE PARTIAL FULFILLMENT OF AWARD OF DEGREE
Of
MASTER OF ENGINEERING
In
(Computer Engineering)
By
Swapnil S. Jagtap
Semester-II Roll No: ******
UNDER THE GUIDANCE OF
Guide Name
(Department of Computer Engineering)
VPCOE, Baramati
DEPARTMENT OF COMPUTER
ENGINEERING
Vidya Pratishthan’s College of Engineering,
Vidyanagari Bhigawan Road
Baramati, Dist. Pune
Pin-413133
2015-2016

2. CERTIFICATE
This is to certify that Mr. Swapnil S. Jagtap has successfully submitted
his seminar report to Department of Computer Engineering, VPCOE,
Baramati, on
Cluster-based Wireless Sensor Network
(WSN) Methods for Secure and Efficient
Data Transmission
During the academic year 2015-2016 in the partial fulfillment towards
completion of First year of
Master of Engineering in Computer Engineering of
Savitribai Phule Pune University, Pune (Maharashtra)
Name Name
Guide PG Co-ordinator
Name Name
Head of Dept. Principal
Date :
Place: VPCOE, Baramati.

3. Acknowledgment
This is to acknowledge and thank all the individuals who played defining role
in shaping this seminar report. Without their constant support, guidance
and assistance this seminar report would not have been completed. Without
their coordination, guidance and reviewing this task could not be completed
alone.
I avail this opportunity to express my deep sense of gratitude and whole
hearted thanks to my guide Guide Name for giving his valuable guidance,
inspiration and encouragement to embark this seminar.
This seminar being conceptual one needed a lot of support from my guide
so that I could achieve what I was set out to get.
I would personally like to thank, Name, PG Seminar Co-ordinator, Com-
puter Department, Name, HOD and our Honorable Principal Name Sir who
creates a healthy environment for all of us to learn in best possible way.
Mr. Swapnil S. Jagtap
M.E. Computer
Roll No. ******

4. Abstract
Secure information transmission is a basic issue for Wireless Sensor Net-
works (WSNs). Clustering is a practical approach to improve the execution
of WSNs. In this paper we study about the safe and efficient data transmis-
sion in Clusterbased Wireless Sensor Networks (CWSNs). Here two Secure
and Efficient data Transmission (SET) protocols are proposed namely (SET-
IBS) and (SET-IBOOS) by using digital signature schemes. The SET-IBS
security depends on the hardness of the discrete logarithm issues. In this pa-
per the feasibility of the SET-IBS and SET-IBOOS protocols is shown with
respect to the security requirements and analysis against various attacks.
The calculations and simulations are given to represent the effectiveness of
the proposed execution over the current secure protocols for CWSNs, as far
as security overhead and energy consumption is considered. A WSN sys-
tem consist of distributed devices using wireless sensor nodes to monitor the
physical or the environmental conditions, such as sound, temperature, air,
vibration and motion. The individual nodes in WSN are capable of sensing
their environment, processing the information locally and sending data to
one or more collection points in WSN. In this process efficient data transmis-
sion is one of the most important issues in WSN. Many WSN are deployed
in extreme physical environments for applications such as military domains,
natural or artificial disasters or certain rescue operations with trustless sur-
roundings. Secure and efficient data transmission is thus especially necessary
and is demanded in many such practical WSNs.

5. Contents
1 Introduction 7
1.1 WSN Network Topologies . . . . . . . . . . . . . . . . . . . . 8
1.2 Components of a WSN Node . . . . . . . . . . . . . . . . . . . 9
1.3 Network Architecture . . . . . . . . . . . . . . . . . . . . . . . 10
2 Literature Survey 11
2.1 Paper Title: A Survey of Security Issues in Wireless Sensor
Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.2 Paper Title: Secure Routing In Wireless Sensor Networks: At-
tacks And Countermeasures . . . . . . . . . . . . . . . . . . . 12
2.3 Paper Title: Routing Techniques in Wireless Sensor Networks:
A Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.4 Paper Title: Balanced energy sleep scheduling scheme for high
density cluster-based sensor networks . . . . . . . . . . . . . . 14
3 Protocols 15
3.1 Steps for SET-IBS Protocol for CWSN . . . . . . . . . . . . . 15
3.2 Protocol operation in SET-IBS . . . . . . . . . . . . . . . . . 16
3.3 Steps for SET-IBOOS Protocol for CWSN . . . . . . . . . . . 19
3.4 Protocol operation in SET-IBOOS . . . . . . . . . . . . . . . 20
3.5 Message Size of Data Transmission . . . . . . . . . . . . . . . 23
4 Attack Models 25
4.1 Passive attack on wireless channel . . . . . . . . . . . . . . . . 25
4.2 Active attack on wireless channel . . . . . . . . . . . . . . . . 25
4.3 Node compromising attack . . . . . . . . . . . . . . . . . . . . 26
5 Comparison 27
6 Conclusion 31

6. List of Figures
1.1 WSN Components . . . . . . . . . . . . . . . . . . . . . . . . 8
1.2 WSN Network Topologies . . . . . . . . . . . . . . . . . . . . 8
1.3 WSN Sensor Node Components . . . . . . . . . . . . . . . . . 9
1.4 Simple Cluster Network Architecture . . . . . . . . . . . . . . 10
3.1 Operation in the proposed system . . . . . . . . . . . . . . . . 16
3.2 Flowchart of the distributed cluster head formation . . . . . . 22
3.3 Message size for transmission compared to the number of nodes 24
5.1 Comparison of FND time in different protocols . . . . . . . . . 28
5.2 Comparison of energy consumption in different protocols . . . 28
5.3 Comparison of the number of alive nodes in different protocols 29

7. List of Tables
3.1 Operations in SET-IBS . . . . . . . . . . . . . . . . . . . . . . 17
3.2 Operations in SET-IBOOS . . . . . . . . . . . . . . . . . . . . 20
5.1 Comparison of characteristics of the proposed protocols with
other secure data transmission protocols . . . . . . . . . . . . 30

8. Chapter 1
Introduction
A wireless sensor network (WSN) is a network system consisting of spa-
tially distributed devices using wireless sensor nodes to monitor environmen-
tal or physical conditions like temperature, humidity, sound, wind speed and
direction, pressure, pollution levels, etc. WSNs were initially designed for
military operations but its applications has been extended to traffic, health,
and many other industrial areas. A WSN consists of a few hundreds to thou-
sands of sensor nodes. The sensor node equipment has a radio transceiver
along with an antenna, a micro-controller, an interfacing electronic circuit,
and an energy source (ie-battery). The size of the sensor nodes can range
from the size of a shoe box to the size of a grain of dust. Their prices also
vary from a few pennies to hundreds of dollars depending on the function-
ality parameters of a sensor like energy consumption, computational speed,
bandwidth and memory.
WSN applications like the streetlights, power grid and water treatment,
wireless sensors offer a lower-cost method for collecting system health data to
reduce energy usage and manage resources in better way. Remote monitoring
covers a wide range of applications by replacing wired systems with wireless
systems for reducing wiring costs and allowing new types of measurement
applications.
The individual sensor nodes are capable of sensing their environments,
processing the data locally and sending data to one or more collection points
in a WSN [16]. Efficient data transmission is the most important issues for
WSNs. Meanwhile, many WSNs are deployed in neglected, extreme and of-
ten harsh physical environments for certain applications, such as military
domains and sensing tasks with unexpected surroundings. Secure and effi-
cient data transmission is thus necessary and is been demanded in many such
practical WSNs.
7

9. A WSN system integrates a gateway that provides wireless connectivity to
the wired world and distributed sensor nodes. The wireless protocol selected
depends on your application requirements. The available standards include
2.4 GHz radios based on either IEEE 802.15.4 standards which are usually
900 MHz.
Figure 1.1: WSN Components
1.1 WSN Network Topologies
WSN nodes are organized in three types of network topologies. In a star
topology, each node connects directly to a gateway. In a cluster tree network,
each node connects to a node higher in the tree, then to the gateway, and data
is routed from the lowest node of the tree to the gateway. To offer increased
reliability, mesh networks feature nodes that connects multiple nodes in the
system and pass data through the most reliable path available. This mesh
link is often referred to as a router.
Figure 1.2: WSN Network Topologies
8

10. 1.2 Components of a WSN Node
In WSN the sensor node contains several technical components. These
include the radio, battery, micro-controller, analog circuit, and sensor inter-
face. When using radio technology, you must make important cooperation
in battery-powered systems, higher data rates and more frequent radio use
consumes more power. Three years of battery life is a minimum requirement,
so many of the WSN systems today are based on low-power consumption.
Because battery life and power management technology are always evolving
and because of the available IEEE 802.15.4 standard, WSN is an interesting
technology.
In addition to long life requirements of the sensor node you must consider
the size and weight of batteries as well as foreign standards for shipping bat-
teries. The wide availability of alkaline, carbon and zinc batteries with low
cost make them a common choice.
To extend battery life, a WSN node is put on sleep mode and periodically
wake-up and transmit data by powering on the radio and then going back
sleep mode to conserve energy. WSN radio technology must efficiently trans-
mit a signal and allow the system to go to sleep with minimal power. This
means the processor must also be able to wake-up and return to sleep mode
efficiently. Microprocessor trends for WSN include reducing power consump-
tion and increasing processor speed. Much like the power consumption, the
radio choice and processing speed compromise is a key concern when select-
ing a processor for WSN. This makes the x86 architecture a difficult choice
for battery-powered devices.
Figure 1.3: WSN Sensor Node Components
9

11. 1.3 Network Architecture
Consider a CWSN consisting of a fixed base station (BS) and a large num-
ber of wireless sensor nodes (SN), which are homogeneous in functionality
and capabilities. The BS is a trusted authority (TA). The sensor nodes may
be exposed by attackers and the data transmission may be interrupted from
attacks on wireless channel. Sensor nodes are grouped into clusters and each
cluster has a cluster-head (CH) sensor node, which is elected autonomously.
Sensor nodes join a cluster depending on the signal strength and transmit the
sensed data to the BS via CH to save energy. The CH perform data fusion
and then transmit data to the BS directly with high energy. In addition all
sensor nodes, CH and the BS are time synchronized with symmetric radio
channels, nodes are distributed randomly, and their energy is constrained.
In CWSN, data sensing, data processing and data transmission consume
energy of sensor nodes. The cost of data transmission is more expensive than
the data processing. Thus, the intermediate node (e.g., a CH) aggregates
data and sends it to the BS is preferred, than the each sensor node directly
sends data to the BS. A sensor node switches into sleep mode for energy
saving when it does not sense or transmit data, depending on the TDMA
(Time Division Multiple Access) control used for data transmission.The pro-
posed SET-IBS and SET-IBOOS are both designed for the same premise of
CWSNs above.
Figure 1.4: Simple Cluster Network Architecture
10

12. Chapter 2
Literature Survey
2.1 Paper Title: A Survey of Security Issues
in Wireless Sensor Networks
The efficiency of the Wireless sensor networks which are mainly used
for military purpose for sending and receiving the code or message [13] is
analyzed in this paper. It determines the open research issues for direction on
security in WSN. Secure routing protocols are considered in key distribution
the node sends the message from one node to base station. Aggregation of
sensor data is secured. It produce less important for low level data to save
energy and produce high security for more sensitive data.
The main purpose of security requirements is to identify the information
and resource from misbehavior and attacks. Symmetric key cryptography is
power consumption in sensor nodes. The open research issues are low energy
cost and high speed. In this efficient and flexible key distribution are to be
designed. There are many routing techniques been designed for WSN. Some
networks are design security as a goal. Wireless sensor network are unsafe
to many kind of attack in secure routing protocols.
Secure routing is a Ad-hoc network similar to sensor network. It depends
on proper key management scheme in WSN. Data aggregation is mainly for
WSN. The nodes are been given pair wise key and other node are in multiple
hops. The cluster head collect all the information and send it to the base
station as required. Sensor nodes are constrained by less energy.
11

13. 2.2 Paper Title: Secure Routing In Wireless
Sensor Networks: Attacks And Counter-
measures
Many routing protocols are been proposed to reduce the energy consump-
tion in the wireless sensor network. But none of them deal with the security
issues in the wireless sensor network [15]. If a Wireless sensor network is
attacked, then it would cause a serious loss.
The two categories of attacks against the sensor networks are Sinkhole
and Hello Flood attacks.
• Sinkhole Attack - It exposes a node in the network, attracts the
neighboring nodes and makes every data to go through it with regards
to the routing algorithm.
• Countermeasure - Geographic protocol is used to avoid sinkhole at-
tack. This protocol uses the localized information and interaction to
construct a topology and also avoid the initiation from the base station.
• Hello Flood attack - An attacker outside the network who has large
transmission power may send a HELLO packet to every node in the
network and make them to believe that it is within the network. So,
attacker can easily steal the data.
• Countermeasure - Each node is provided with an ID and during data
transmission each node should authenticate its neighboring node using
Identity verification protocol to avoid Hello Flood attack. Multipath
protocol can be used to avoid exposed nodes. In this protocol the data
is routed over ‘n’paths and the nodes in it are disjoint.
12

14. 2.3 Paper Title: Routing Techniques in Wire-
less Sensor Networks: A Survey
In this paper [14], the major issue in wireless sensor network is energy con-
sumption which would reduces the lifetime of the network. Since the entire
sensor nodes are battery powered, certain steps should be taken to conserve
the battery power. Clustering could reduce the energy consumption to some
extent.
Another method to reduce the energy consumption is using routing tech-
niques. The data sensed by the sensor nodes are sent to the base station by
some strategy which will reduce the energy consumption to a great extent.
Routing in wireless sensor network has three classification and they are
• Flat-based routing - all the nodes have equal functionality in the
network
• Hierarchical-based routing - nodes have different functionality in
the network
• Location-based routing - position of the nodes in the network de-
cides the functionality.
In all the above routing techniques the best path that consumes less
energy for the data transmission is found and data is sent through it. If any
node in the established path is damaged or failed then the routing algorithm
itself should accommodate a new path to the base station. The main aim
is reducing the energy consumption of the nodes in the network without
compromising the data delivery.
13

15. 2.4 Paper Title: Balanced energy sleep schedul-
ing scheme for high density cluster-based
sensor networks
In this paper [12], the concept analyzed is conserving battery power in
sensor network to achieve this nodes which are ideal can be put to sleep mode
so that the energy can be used by only those nodes which are active. Three
scheduling schemes are described, which are Balanced-energy Scheduling
scheme (BS), Randomized Scheduling scheme (RS), Distance based Schedul-
ing scheme (DS).
Randomized Scheduling scheme (RS) selects the nodes randomly, which
are ideal and puts them to sleep mode. Distance based Scheduling scheme
(DS) selects the ideal nodes with respect to the distance of those nodes from
the cluster head. Balance-energy scheduling scheme (BS) maintains the av-
erage energy consumption of all the nodes in the cluster to be same. The
mechanism used to put the ideal nodes to sleep has to be aware of putting
only the ideal nodes and not the nodes which are active.
Timer will be provided to those nodes which are put to sleep which will
consume very low energy in order to keep track of the time duration of the
sleeping nodes.
14

16. Chapter 3
Protocols
3.1 Steps for SET-IBS Protocol for CWSN
An IBS protocol implemented for CWSN performs the following opera-
tions, setup at the Base Station (BS), key extraction and signature signing
of the data sending nodes and verification of the data receiving nodes.
• Setup: The BS generates a master key msk and public key parameters
param for the private key generator (PKG), and gives them to all sensor
nodes.
• Extraction: A sensor node generates a private key sekID associated
with the ID using msk.
• Signature signing: For the message M, time-stamp t and a signing
key θ, the sending node generates a signature SIG.
• Verification: From the ID, M and SIG, the CH outputs “accept”if
SIG is valid, and outputs “reject”otherwise.
15

17. 3.2 Protocol operation in SET-IBS
After initialization of the the protocol, SET-IBS operates in rounds during
communication. Each round consists of a setup phase and a steady-state
phase. All sensor nodes know the starting and ending time of each round
because of the time synchronization.
Figure 3.1: Operation in the proposed system [1]
The operation of SET-IBS is divided into rounds as shown in Figure 3.1,
which is similar to other LEACH-like protocols. Each round has a setup
phase for constructing clusters from CH and a steady-state phase for trans-
mitting data from sensor nodes to the BS. In each round, the time-line is
divided into consecutive time slots by the TDMA (time division multiple
access) control [3]. Sensor nodes transmit the sensed data to the CH in each
frame of the steady-state phase. Nodes are randomly elected as CH for each
round and other non-CH sensor nodes join clusters depending on the highest
received signal strength of CH. In order to elect CH in a new round, each
sensor node determines a random number and compares it with a threshold.
If the value is less than the threshold the sensor node becomes a CH for
the current round. In this way, the new CH are self-elected by the sensor
nodes themselves only on their local decisions. Therefore, SETIBS functions
without data transmission with each other in the CH rotations.
16

18. Table 3.1: Operations in SET-IBS
Setup phase
Step 1. BS ⇒ Gs : IDbs, Ts, nonce
Step 2. CHi ⇒ Gs : IDi, Ts, adv, σi, ci
Step 3. Lj → CHi : IDi, IDj, Ts, join, σj, cj
Step 4. CHi ⇒ Gs : IDi, Ts, sched(IDj/tj), σi, ci
Steady state phase
Step 5. Lj → CHi : IDi, IDj, tj, C, σj, cj
Step 6. CHi → BS : IDbs, IDi, Ts, F, σi, ci
Notations -
⇒, → : Broadcast and unicast transmission.
Lj, CHi, Gs : A leaf node, a cluster head, and the set of
sensor nodes in the network.
Ts, tj : Time-stamps denoting the time slot for transm-
ission in setup and steady-state phases.
IDi, IDbs : The ID of a sensor node i or the BS.
C, F : Encrypted sensed data and aggregated data.
adv, join, sched : Message string types which denote the adverti-
sement, join request, and allocation messages.
σi, ci : The ID-based digital signature concatenated
with data from node i.
Table I shows all steps in one round of SET-IBS. The setup phase consists
of four steps from Step 1 to 4, and the steady-state phase consists of the last
two steps 5 and 6. In the setup phase, the time-stamp Ts and node IDs
are used for the signature generation. Whereas, in the steady-state phase,
the time-stamp ti is used for the signature generation securing the cluster
communications, and Ts is used for the signature generation securing the CH
to BS data transmission.
In Step 1, at the beginning of the setup phase of a new round, the BS
first broadcasts its ID, a nonce (number used once), and the starting time
Ts of the current round to all sensor nodes, which is used for the signature
signing and verification in the setup phase.
In Step 2, a sensor node decides to become a CH for the current round,
based on the threshold T(n) compared with numbers from 0 to 1, which is
set as follows:
17

19. T(n) =
ρ
1 − ρ(r mod 1
ρ
)
·
Ecur(n)
Einit(n)
∀n ∈ Gn
T(n) = 0 ∀n ∈ Gn
The above equation computes the threshold T(n) in node n is based on the
LEACH protocol. Note that we improve the dynamic clustering algorithm
rather with multiplying the ratio of residual energy of the current sensor
node (i.e., Ecur(n)
Einit(n)
) to increase the energy efficiency in the clustering where,
Ecur(n) is the current energy and Einit(n) is the initial energy of the sensor
node. ρ is a priori determined value which stands for the desired percentage
of CHs during one round (e.g., ρ=10%), r is the current round number, and
Gn is the set of sensor nodes that have not been CH in the last 1/ρ rounds.
If the value of determined number is less than the threshold then the sensor
node elects itself as a CH. The sensor node who become a CH broadcasts the
advertisement message (adv) to the neighboring nodes in the network which
is concatenated with the signature σi, ci .
In Step 3, the sensor node, which decides to be a leaf node selects a CH to
join the cluster based on the largest received signal strength of adv messages.
Then, it communicates with CHi by sending a join request (join) message,
which is concatenated with the destination CH’s ID IDi, its own ID IDj,
time-stamp Ts, and the digital signature σj, cj .
In Step 4, a CHi broadcasts an allocation message to its cluster members
for communication during the steady-state phase including a time schedule
sched(IDj/tj) by the TDMA control, yet to be concatenated with the
signature.
Once the setup phase is complete, the network system turns into the
steady-state phase in which sensed data is transmitted from sensor nodes to
the BS. In Step 5, according to the TDMA schedule from Step 4, each leaf
sensor node j transmits the encrypted data C in a packet IDj, tj, C, σj, cj
to its CH, which is concatenated with a digital signature in a time slot tj,
where the sender ID IDj with tj is the destination identifier for the receiver
CH. In this way, each CH collects messages from all members in its cluster,
aggregates and fuses data.
In Step 6, CH send the aggregated data F to the BS, to be concatenated
with the digital signature. The steady-state phase consists of multiple cycles
of data transmissions from leaf nodes to the CH and is exceedingly long
compared to the setup phase.
18

20. 3.3 Steps for SET-IBOOS Protocol for CWSN
An IBOOS protocol implemented for CWSN performs the following four
operations, setup at the Base Station (BS), key extraction and offline signing
at the Cluster Head (CH), online signing of the data sending nodes, and
verification of the receiving nodes.
• Setup: The BS generates a master key msk and public parameters
param for the private key generator (PKG), and broadcast them to all
sensor nodes.
• Extraction: From an ID string, a sensor node generates a private key
sekID associated with the ID using msk.
• Offline signing: From public parameters and time-stamp t, the CH
generates an offline signature SIGoffline, and transmit it to the leaf
nodes in its cluster.
• Online signing: From the private key sekID, SIGoffline and message
M, a sensing node (leaf node) generates an online signature SIGonline.
• Verification: From the ID, M and SIGonline, the cluster head outputs
“accept”if SIGonline is valid, and outputs “reject”otherwise.
19

21. 3.4 Protocol operation in SET-IBOOS
Table 3.2: Operations in SET-IBOOS
Setup phase
Step 1. BS ⇒ Gs : IDbs, Ts, nonce
Step 2. CHi ⇒ Gs : IDi, Ts, adv, σi, zi
Step 3. Lj → CHi : IDi, IDj, Ts, join, σi, zj
Step 4. CHi ⇒ Gs : IDi, Ts, alloc(IDj/tj/σj), σi, zi
Steady state phase
Step 5. Lj → CHi : IDi, IDj, tj, C, σj, zj
Step 6. CHi → BS : IDbs, IDi, Ts, F, σi, zi
Notations -
⇒, → : Broadcast and unicast transmission.
Lj, CHi, Gs : A leaf node, a cluster head, and the set of
sensor nodes in the network.
Ts, tj : Time-stamps denoting the time slot for trans-
mission in setup and steady-state phases.
IDi, IDbs : The ID of a sensor node i or the BS.
C, F : Encrypted sensed data and aggregated data.
adv, join, alloc : Message string types which denote the adver-
tisement, join request, and allocation messages.
σj : The offline signature of node i concatenated
with data.
σi, zi : The online signature of node i concatenated
with data.
The proposed SET-IBOOS operates similar to SETIBS. SET-IBOOS
works in rounds during communication, and the self-elected CH are based
on their own decisions, thus it operates without data transmission in the CH
rotations. For the IBOOS key management in SET-IBOOS, the offline signa-
tures are generated by the CH which are used for the online signing at the leaf
nodes. Table II shows the full steps of SET-IBOOS in one round in which the
setup phase is from Step 1 to 4, and the steady-state phase is of Step 5 and 6.
20

22. Step 1 in Table II is similar to that in Table I. However, the difference in
steps 2 and 3 is the change from the IBS to the online signature σi, zi for
the IBOOS scheme.
In Step 4, a CHi first generates the offline signatures for the leaf nodes in
its cluster. It then broadcasts an allocation message alloc(IDj/tj/σj) to its
cluster members for the secure communication during the steady state phase
concatenated with the online signature. The allocation message consists of a
time schedule composed by the TDMA control which allocates a time-stamp
with an offline signature (IDj/tj/σj) for node j.
Once the setup phase is over, the network system turns into the steady-
state phase in which data is transmitted to the Base Station (BS). The
steady-state operates similarly to that in steps 5 and 6 of Table I, where the
IBS is changed into the online signature for the IBOOS scheme.
21

23. Figure 3.2: Flowchart of the distributed cluster head formation [3]
22

24. 3.5 Message Size of Data Transmission
Here we do the quantitative calculation of the message packet size on
data transmission in the steady-state phase of the protocols for comparison.
The proposed SET-IBS, the message packet size for node j equals to
|IDj| + |ti| + |C| + |σj| + |h(C ti θ)|
|h(C ti θ)| is a hash value, which is 20 bytes when SHA-1 is used. Al-
though most of existing WSN constructed in real world use no more than
200 nodes, a large scale WSN could consist of hundreds of nodes or more in
the future. Thus we set the length of a node ID as 2 bytes. In addition, the
time-stamp |ti| is very small like 2 bytes, and cipher text |C| is assumed as
20 bytes. The total message size of a transmission packet is 44 + |σj| bytes,
whereas, |σj| is variable.
In SET-IBOOS, the message packet size for node j equals to
|IDj| + |tj| + |C| + |σj| + |zj|
|IDj| and |tj| are similar to that of SET-IBS as 2 bytes by each, and
|C| is assumed as 20 bytes. In the online signature σj, zj , the length of
|z| = |σj + (hs modq)| depends on the size of q, which is set to 160 bits long
to achieve a similar security level of SET-IBS, because the offline signature σj
is a negative exponential value of the cyclic group G’s generator g that is very
small. For the other part of the signature σj, zj ,|σj| is the exponentiation
to the power σj, from the negative exponential function of the generator g,
thus its value is very small, which is assumed as 2 bytes at most. Therefore,
the total message size of a data packet is 46 bytes in SET-IBOOS.
23

25. Figure 3.3: Message size for transmission compared to the number of nodes
Figure 3.3, shows the message sizes in different protocols for data trans-
mission which achieve a similar security level to RSA-1024 by concerning
the number of sensor nodes. We can see that the proposed IBS has smaller
message size than multi-level based protocol. At the same time, it generates
larger message size as compared to Sec-LEACH. However, the orphan node
problem is fully solved in IBS [3]. We can also see that the proposed IBOOS
has the smallest message size than all the other protocols available for WSN.
24

26. Chapter 4
Attack Models
To assess the security of the proposed protocols we have to analyze the
attack models in WSN which threaten the proposed protocols and when
an attacker exists in the network. So we group attack models into three
categories as follows and study how these attacks may be applied to affect
the proposed protocols.
4.1 Passive attack on wireless channel
Passive attackers perform eavesdropping at any point of the network
or even the whole communication of the network. Thus, they can undertake
traffic analysis or statistical analysis based on the monitored or eavesdropped
messages.
4.2 Active attack on wireless channel
Active attackers have more ability than passive attackers, which can
tamper with the wireless channels. So, the attackers can forge, reply and
modify messages. Especially in WSN various types of active attacks can
be triggered by attackers such as sinkhole and wormhole attack, selective
forwarding attack, bogus and replayed routing information attack, HELLO
flood attack, and Sybil attack.
25

27. 4.3 Node compromising attack
Node compromising attackers are the most powerful attackers against
the proposed protocols. The attackers can physically expose sensor nodes
by which they can access the information stored in the endangered nodes,
e.g., the security keys. The attackers also can change the state and behavior
of the exposed sensor node whose actions may be varied from the premier
protocol specifications.
The proposed SET-IBS and SET-IBOOS provide different types of se-
curity services to the communication for CWSNs, in both setup phase and
steady-state phase. The encrypted message provides confidentiality, the hash
function provides integrity, the nonce and time-stamps provide freshness and
the digital signature provides authenticity and non-repudiation.
26

28. Chapter 5
Comparison
The energy consumption for the security overhead and extending the
network lifetime are essential for the proposed SET-IBS and SET-IBOOS
protocols. In order to evaluate the energy consumption of the computational
overhead for security in communication we consider three measures for the
performance evaluation: Network lifetime, the number of alive nodes and
system energy consumption. For the performance evaluation we compare the
proposed SET-IBS and SET-IBOOS with LEACH protocol and SecLEACH
protocol.
• Network lifetime (the time of FND) - The most general metric in this
paper, the time of FND (first node dies) which indicates the duration
that the sensor network is fully functional. Therefore, increase the time
of FND in a WSN means to extend the network lifetime.
• The number of alive nodes - The capability of collecting infor-
mation in a WSN depends on the set of alive nodes (nodes that have
not failed or orphan nodes). Evaluate the functionality of the WSN
depending on counting the number of alive nodes in the network.
• Total system energy consumption - It refers to the amount of
energy consumed in a WSN. Evaluate the energy consumption in secure
data transmission protocols.
Figure 5.1 illustrates the time of FND (first node dies) using different
protocols. Apply confidence (as 90%) intervals to the simulation results.
Figure 5.3 shows the comparison of system lifetime using SETIBS and SET-
IBOOS versus LEACH and SecLEACH protocol. The simulation results
show that the system lifetime of SET-IBOOS is longer than that of SET-IBS
27

29. and SecLEACH protocol. The time of FND in both SET-IBS and SET-
IBOOS protocol is shorter than that of LEACH protocol due to the security
overhead on computation cost of the IBS process.
Figure 5.1: Comparison of FND time in different protocols
Figure 5.2: Comparison of energy consumption in different protocols
28

30. Figure 5.3: Comparison of the number of alive nodes in different protocols
Figure 5.2 illustrates the energy of all sensor nodes in the network which
also indicates the balance of energy consumption in the network. Figure 5.3
shows the comparison of alive nodes number in which the proposed SET-
IBS and SET-IBOOS protocols versus LEACH and Sec-LEACH protocols.
The results show that the proposed IBS and IBOOS protocols consume more
energy than LEACH protocol because of the communication and computa-
tional overhead for security of IBS or IBOOS process. However, the proposed
IBOOS protocol has a better balance of energy consumption than that of Se-
cLEACH protocol.
Here we summarize the characteristics of the proposed IBS and IBOOS
protocols. Table III shows a general summary of comparison of the IBS
and IBOOS protocols with other ones in which metrics are used to evaluate
whether a security protocol is appropriate for CWSNs. We explain each
metric as follows:
• Key management: the key cryptography is used to achieve secure
data transmission, which consist of symmetric and asymmetric key
based security.
• Neighborhood authentication: is used for secure access and data
transmission to nearby sensor nodes by authenticating with each other.
Here, “limited”means the amount of neighborhood authentication where
only the nodes with the shared pairwise key can authenticate each
other.
29

31. Table 5.1: Comparison of characteristics of the proposed protocols with other
secure data transmission protocols
SET-IBS / SET-IBOOS Other Protocols
Key Asymmetric Symmetric
management
Neighborhood Yes Limited
authentication
Storage Comparatively low Comparatively high
cost
Network Comparatively high Comparatively low
scalability
Communication Deterministic Probabilistic
overhead
Computational Comparatively high Low High
overhead
Attack Passive and Active attacks on wireless channel
resilience
• Storage cost: it represents the requirement of the security keys stored
in sensor nodes memory.
• Network scalability: this indicates whether a protocol is able to scale
without compromising the security requirements. In the secure data
transmission with a symmetric key management the larger network
increases the more orphan nodes in the network and vice versa.
• Communication overhead: the security overhead in the data pack-
ets during communication.
• Computational overhead: the energy cost and computation effi-
ciency for verification of the certificates or signatures for security.
• Attack resilience: the types of attacks that security protocol can
protect against.
30

32. Chapter 6
Conclusion
We first studied about the sensor node, sensor network and then the
cluster network for WSN. We then reviewed the data transmission issues and
the security issues in CWSN. The need of the symmetric key management
for secure data transmission has been talk about. We then demonstrate
two secure and efficient data transmission protocols respectively for CWSN,
SET-IBS and SET-IBOOS protocols. In the evaluation section, we provided
feasibility of the proposed IBS and IBOOS protocols with respect to the
security requirements and analysis against routing attacks. IBS and IBOOS
protocols are efficient in communication and applying the ID-based crypto-
system, which gains security requirements in CWSN as well as solved the
orphan node problem in the network with the symmetric key management.
The comparison results show that the proposed IBS and IBOOS protocols
have better performance than existing secure protocols for CWSN. With
respect to both communication and computation costs we pointed out the
merits that using IBOOS with less auxiliary security is preferred for secure
data transmission in CWSN.
31

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