Secure Data Transmission for Cluster based WSN
using Identity based Signatures
Thaznim Thaj
M.Tech Student,
School of Computer Sciences,
Mahatma Gandhi University
Abstract—Wireless Sensor Networks (WSN) provides a bridge
between the real physical and virtual world which monitors
physical and environmental conditions. It contributes a wide
range of applications to industry, health-care, science, utilities
and area monitoring. Data security and authentication are the
crucial security requirements in Wireless Sensor Networks.
Clustering method effectively distributes network energy and
applies aggregation technique in the network. Clustering in
Wireless Sensor Networks can greatly contribute to overall
system scalability, lifetime and energy efficiency. Secure and
efficient data transmission can be achieved by using Digital
Signature. The main Principle is to authenticate the encrypted
data packets, by applying signature, which are efficient in data
transmission and applying the key management for security.
Keywords— Cluster-based WSNs, ID-based digital signature,
I. INTRODUCTION
Wireless sensor networks provide efficient methods of
collecting valuable data from the surroundings for use in
different applications. Hence the popularity of wireless sensor
networks (WSNs) is increasing continuously in different
domains of daily life. The network is composed of randomly
deployed sensor nodes, which are able to collect data of
various types from the deployment field. Sensed data are then,
communicated to the base station (BS) through wireless link.
The BS represents a downstream of all information coming
from the sensor nodes. Routing in WSNs is the vital
functionality which allows the flow of information generated
by sensor nodes to the base station. WSNs suffer from many
constraints, including low computation power, limited energy
resources, small memory and the use of secure-less wireless
communication channels. These constraints make security in
wireless sensor network a challenge.
According to the network topology, there are two
categories of Wireless Sensor Networks: flat and hierarchical
WSNs. In flat WSNs, all sensor nodes are in the same level of
privilege; they are all charged of sensing and communication
tasks. Also, data messages are communicated in a multi-hop
policy. However, in hierarchical WSNs (HWSN) the network
is organized in clusters. Each cluster contains one special node
called cluster head (CH), and its member nodes.
Clustering is an energy efficient method which divides
sensor nodes into many clusters. For each cluster there is a
cluster-head. The routing is from cluster-head sensor nodes to
the base station (BS).CH is the router of data sent by its
members to the BS. In Cluster based WSN, member nodes
Shyni S.T
Assistant Professor
School of Computer Sciences
Mahatma Gandhi University
sleep the most of time to save energy. Clustering algorithms
for sensor networks improves network scalability by handling
the important problems regarding the size and mobility of the
network. They vary according to the overall network
architecture, node deploying methods and based on the
characteristics of the CH node. The number of cluster
members will vary according to the application. A cluster
head is a node which is very rich in energy resources.
The Cluster Heads perform data aggregation, and transmit
data to the base station directly with comparatively high
energy. In addition, all the sensor nodes and the BS are time
synchronized with symmetric radio channels, the nodes are
distributed randomly, and their energy is constrained. In
Cluster based WSNs, sensing, processing, and transmission
consume energy of the sensor nodes. The cost of data
transmission is expensive than that of data processing. Thus,
the method that the Cluster head node aggregates data and
sends it to the sink node is preferred than the method that each
sensor node directly sends data to the BS. For energy saving,
sensor node switches into sleep mode when it does not sense
or transmit data. This is based on the time-division multiple
access (TDMA) control used for data transmission.
The low-energy adaptive clustering hierarchy (LEACH)
protocol [2] is an effective and widely known protocol to
reduce and balance the total energy consumption for CWSNs.
To reduce the quick energy consumption of the set of CHs,
LEACH randomly rotates CHs within all sensor nodes in the
network, in each round. LEACH results an improvement in
network lifetime. Providing security in leach protocol is a
tedious work. Secure and efficient data transmission can be
achieved by using identity based Digital Signature. The main
Principle is to authenticate the encrypted data packets, by
applying id based digital signatures which are efficient in data
transmission and applying the key management for security.
In Identity based Cryptographic schemes nodes uses their own
ID information as keys. ID based schemes eliminate the need
for certificate and ensure security and authentication. This
reduces the expensive computation and verification process
required.
II. RELATED WORKS
An exhaustive literature survey has been conducted to
identify related research works conducted in this area.
Abstracts of some of the most relevant research works are
included below.
A. An Application Specific Protocol Architecture for Wireless
Microsensor Networks
LEACH, protocol architecture for microsensor networks
combines the ideas of energy-efficient cluster-based routing
and application-specific data aggregation. This provides good
performance in terms of system latency, lifetime and
efficiency. In LEACH there is a distributed cluster formation
technique which enables organization of large numbers of
nodes, adaptive clustering algorithms and rotating cluster head
positions to distribute the energy load evenly among all the
nodes. Also there are techniques to enable distributed signal
transmission to save communication resources.
In LEACH, the nodes themselves create local clusters. In
each cluster one node acts as the cluster head. All non-cluster
head nodes send their data to the CH, while the cluster head
node collects data from all the cluster members, performs data
fusion, and transmits data to the remote Base Station.
Therefore, being a cluster head is much more energy intensive
than being a non-cluster head node.
B. PEGASIS: Power Efficient Gathering in Sensor
Information Systems
PEGASIS protocol is based on the chain structure. Cluster
head is selected randomly from the dedicated chain and
accountable for data transmission to the BS. Major drawback
of this algorithm is that it needs the global knowledge of the
network, based on which chain can be constructed using
greedy algorithm. There is a proper load matching as a sensor
node receive the data from its neighbor, available in the chain,
aggregate the same with own data and send to the another
neighbour node which is the part of chain. Another drawback
of PEGASIS is the significant delay. It is due to the fact that
the data have to be sequentially transmitted in the chain and
the cluster head waits until all the messages are received
before transmitting to the BS.
C. Identity-Based Cryptosystems and Signature Schemes
The idea of identity based cryptography is to enable a user
to use any arbitrary string that uniquely identifies him as his
public key. Identity based cryptographic scheme serves as an
efficient alternative to Public Key Infrastructure (PKI) based
systems.
An identity-based scheme resembles an ideal mail system:
If you know somebody's name and address you can send him
messages that he can read, and you can verify the signatures
that he could have produced. It makes the cryptographic
aspects of the communication almost transparent, and it can be
used effectively by a user who knows nothing about keys or
protocols.
ID based encryption is a type of public key encryption in
which public key of a user is some unique information about
the user. Any party to generate a public key from known ID,
Private Key Generator (PKG) generates corresponding private
key. To operate PKG, first generate a master public key and
retains a master private key. If master public key is given, any
party can compute a public key corresponding to ID by
combining master public key with ID. To obtain private key,
the authorized party use PKG which uses master private key
to generate ID.
In the case of ID-based signature (IBS), verification takes
only the identity together with the message and signature pair
as input and executes the algorithm directly. This is different
from the traditional public-key cryptography, in which an
extra certificate verification algorithm is needed which is
equivalent to the process of two signatures verification.
Identity-based cryptography could particularly be suitable for
WSN. The absence of certificate eliminates the costly
certificate verification process.
D. Design and Implementation Issues of Clustering in WSN
Clustering offers a wide range of advantages for a sensor
network but it has some drawbacks, issues and challenges.
Issues related to Node Mobility, Traffic Load, Overlapping
Clusters, Load Balancing, Dynamic Cluster Control, Intercluster Coordination, Data Aggregation, Fault Tolerance,
Scalability, Number of Clusters, etc. are to be considered.
The decision of a sensor node to become cluster head or
to join an existing cluster is typically based on the following
metrics.
1) Time: A node may become a CH on a time dependable
basis. For example a CH may be the first node in its
neighborhood that declares itself as a CH.
2) Probability: A node may become a CH depending on a
probabilistic measure. The probability may depend on the
number of nodes in the network , global aggregate energy,
local residual energy, number of times the nodes has been a
CH, cluster size etc.
3) Weight: A weight is an application specific number
assigned to every node in the network. The weight may
depend on multiple measures such as the node degree,
distance to neighbours, movement speed, and energy left
capabilities. A node in the sensor network may become a CH
if it has the highest weight among a group of nodes.
4) Semantics: Semantic refer to the relationship between pairs
of nodes or among nodes in a group. Semantic properties
include distance between nodes, paths available between
nodes, relative mobility, and event type or location attribute
detected. Clusters are formed based on similar semantic
properties of nodes.
The decision process may depend on more than one of the
above metrics. The nodes are grouped based on the semantic
information and the CH is chosen depending on the weight.
E. On-Line/Off-Line Digital Signatures
In order to reduce the computational cost of signature
generation, online/offline signature is preferable in WSN.A
new type of signature scheme is introduced which consists of
two stages. The first stage is off-line, before the message to be
signed. The second stage is performed on-line, after the
message to be signed is known, and is supposed to be very
fast. In WSN, the offline stage is activated at the base station,
while the online stage is activated in the WSN node. The
online stage is comparatively very fast, and hence can be
efficiently executed.
III. CLUSTER BASED WIRELESS SENSOR NETWORK
A. Architecture
In clustered wireless sensor network, sensor nodes are
grouped into clusters, and each cluster has a cluster Head
(CH) as shown in fig 1. The Cluster Head is elected
autonomously. The CHs executes data aggregation, and
transmit data to the BS straight away with reasonably high
energy.
Fig.2 Protocol Operation
This property avoids the requirement of using
certificates and associates an implicit public key (user
identity) to each user within the system. In the case of IDbased signature, verification takes only the identity together
with the message and signature pair as input and executes the
algorithm directly. Fig 3 illustrates the process of encryption
and decryption using the keys generated. Private Key is
generated from nodes ID and the mask (msk) function of Base
station (BS). Similarly, public key is generated from msk
function of Cluster head. Security can be provided by
applying keys to the data.This can greatly reduce computation
cost and communication overhead, which is an important
factor in the design of WSN.
Fig.1 Cluster based Wireless Sensor Network
B. Cluster Formation
Nodes that are decided to become CHs in that round
broadcast an advertisement message (adv) to all sensor nodes
in the network, which is concatenated with the digital
signature. Then the nodes that decide to be leaf nodes pick a
CH to join in, which is based on the largest received signal
strength of adv message. It is then communicated with the CH
by sending a join request (join) message. After that the CHs
broadcast an allocation message to their cluster members. The
communication between CH and leaf nodes takes place during
the steady-state phase.
C. Protocol Operation
Each round consists of a setup phase and a steady-state
phase shown in fig 2. Let all sensor nodes know the starting
and ending time of each round because of the time
synchronization. Setup phase is for constructing clusters and a
steady-state phase for transmitting data from sensor nodes to
the BS. In each round, TDMA control divides the timeline
into consecutive time slots. Sensor nodes transmit the sensed
data to the CHs in each frame of the steady-state phase. Leaf
nodes send their data to the Cluster head. Cluster head then
aggregates all the data and is transmitted to the BS.
IV. IDENTITY BASED SIGNATURE
In an ID-based cryptography, public key of each user
is easily computable from a string corresponding to the user’s
identity.
Fig.3 Identity based Signature
V. SIMULATION
NS2 is an open-source event-driven simulator
designed specifically for research in computer communication
networks. NS2 can be used for simulating wired as well as
wireless network functions and protocols (e.g.,routing
algorithms, TCP, UDP). NS2 provides users with a way of
specifying such network protocols and simulating their
corresponding behaviours. Design of NS2 is illustrated in the
fig 4.
This system can be extended such that CH node can
transmit data to the BS by forwarding its data to its neighbour
nodes, in turn the data are sent to the BS.
REFERENCES
[1] Huang Lu, Jie Li, and Mohsen Guizani, “Secure and Efficient Data
Transmission for Cluster-Based Wireless Sensor Networks,”IEEE Trans.
Parallel and Distributed Systems, vol. 25, no. 3, March 2014
[2] W. Heinzelman, A. Chandrakasan, and H. Balakrishnan, “An ApplicationSpecific Protocol Architecture for Wireless Microsensor Networks,” IEEE
Trans. Wireless Comm., vol. 1, no. 4, pp. 660-670, Oct. 2002
[3] S. Lindsey and C. S. Raghavendra, “PEGASIS: power efficient gathering
in sensor information systems”, Proc.IEEE International Journal of Advanced
Fig.4 NS2 Design
Research in Computer and Communication Engineering
Aerospace
Conference, Big Sky, MT, USA, pp 1125-1130, March 2002
[4] A. Shamir, “Identity-Based Cryptosystems and Signature Schemes,” Proc.
To use NS-2, a user programs in the OTcl script
language. An OTcl script will do the following.
 Initiates an event scheduler.
 Network topology set up using the network objects.
 Inform traffic sources when to start/stop transmitting
packets through the event scheduler.
Flow of events for a Tcl file in NS2 is illustrated in
fig 5.
Fig.5 Flow of Events for a Tcl File
VI. CONCLUSION AND FUTURE ENHANCEMENT
Secure routing in cluster based wireless sensor network is
achieved by applying the ID-based cryptosystems. It reduces
the communication overhead inside clustered wireless sensor
network.
Advances in Cryptology (CRYPTO), pp. 47-53, 1985
[5] K. Pradeepa, W.R. Anne, and S. Duraisamy, “Design and Implementation
Issues of Clustering in Wireless Sensor Networks,”Int’l J. Computer
Applications, vol. 47, no. 11, pp. 23-28, 2012.
[6] S. Even, O. Goldreich, and S. Micali, “On-Line/Off-Line Digital
Signatures,” Proc. Advances in Cryptology (CRYPTO), pp. 263-275, 1990.