Enhancing the Life Time of Wireless Sensor Networks Using SOBAS
1
2
K.Dhana Bhavithra, PG Student, Kongu Engineering College, Perundurai
dhanabhavithrait@gmail.com
Dr.S.Anandamurugan, Assistant Professor (SLG), Kongu Engineering College, Perundurai
valasuanand@yahoo.com
Abstract:
for malicious nodes to eavesdrop, intercept, or
loose
be made aware of the presence of the network.
is
Thus, SOBAS provides energy efficient and an
introduced, to securely synchronize the events in
effective technique to securely synchronize the
the network, without the transmission of explicit
nodes on the data delivery path in the network.
The
Secure
Synchronization
sOurce-BAsed
(SOBAS)
protocol
synchronization control messages. Nodes use
their local time value and initial vector value as a
Key Words:
SOBAS, Loose Synchronization,
one-time dynamic key to encrypt each message.
SOBAS provides an effective dynamic en-route
Wireless Sensor Network, Dynamic En-Route
filtering mechanism, where the malicious data is
Filtering.
filtered
from
the
network.
Instead
of
1 Introduction
synchronizing each sensor globally, SOBAS
focuses on ensuring that each source node is
synchronized with the sink such that event
reports generated by the sink are ordered
properly. Hence, the objective of the SOBAS
protocol is to provide a loose synchronization
protocol for WSNs rather than a perfect
synchronization among the nodes. With loose
synchronization, it reduces the number of control
messages needed for a WSN to operate
providing the key benefits of reduced energy
consumption as well as reducing the opportunity
Wireless Sensor Networks serves as the most
attractive field for many researchers. But it
consists of many micro devices called sensor
nodes which are powered by batteries. They are
widely employed in many applications such as
environment monitoring, earthquake detection,
etc where replacement of batteries is not
practical. Therefore they should be managed
carefully to minimize the consumption of
energy. Sensor node is a device that includes
three basic components:

Sensing subsystem

Processing subsystem

Wireless communication system
public key server directory to allow public key
1.1 KEY
sharing. PGP server directory keys may be
In cryptography, a key is a variable value
updated but not removed.
that is applied using an algorithm to a string or
block of unencrypted text to produce encrypted
2 LITERATURE REVIEW
text, or to decrypt encrypted text. The length of
the key is a factor in considering how difficult it
Pottie G.J and Kaiser W.J (2000) proposed
that the opportunities for Wireless Integrated
will be to decrypt the text in a given message.
Network Sensors (WINS) depend on the
development of scalable, low cost, sensor
1.1.1 Private Key
network architecture. This requires that sensor
In cryptography, a private or secret key is
an encryption/decryption key known only to the
party or parties that exchange secret messages.
In traditional secret key cryptography, a key
would be shared by the communicators so that
each could encrypt and decrypt messages. The
risk in this system is that if either party loses the
key or it is stolen, the system is broken.
A
more recent alternative is to use a combination
of public and private keys. In this system, a
public key is used together with a private key.
information be conveyed to the user at low bit
rate with low power transceivers. Continuous
sensor signal processing must be provided to
enable constant monitoring of events in an
environment. By coming to decisions on these
events, short message packets suffice. Future
applications of distributed embedded processors
and sensors will require massive numbers of
devices. Conventional methods for sensor
networking would present impractical demands
on cable installation and network bandwidth.
Through processing at source, the burden on
1.1.2 Public Key
communication system components, networks,
A public key may be placed in an open
and human resources are drastically reduced.
access directory for decryption of the digital
The physical considerations that lead to the
signature of the sender; the public key of the
design of densely distributed sensor networks,
message
recipient
message.
Public
encrypts
Key
the
sender’s
Infrastructure
(PKI)
and reviewed the advantages of layered and
heterogeneous
processing/networking
produces public and private keys. The open
architectures for these applications. The close
access public key may also be e-mailed to
intertwining of processing of networking is a
trusted contacts and users. Pretty Good Privacy
central feature of systems that connect the
(PGP) is a popular form of public key
physical and virtual
cryptography. Public PGP keys are housed in a
platforms are now available that will more easily
worlds. Development
enable a broader community to engage in
event
fundamental research in networking and new
expenditure
applications,
functionality.
advancing
us
towards
truly
pervasive computing.
detection
with
and
minimum
congestion
energy
resolution
Uluagac S, Lee C, Beyah R, and
Akan O and Akyildiz I (2005) proposed that
Copeland J (2008) proposed that Wireless
WSN are event based systems that rely on the
Sensor Networks (WSNs) are adhoc networks
collective effort of several micro sensor nodes.
comprised mainly of small sensor nodes with
Reliable event detection at the sink is based on
limited resources, and can be used to monitor
collective in- formation provided by source
areas of interest. It proposes a solution for
nodes and not on any individual report. Hence,
securing heterogeneous hierarchical WSNs with
conventional end-to-end reliability definitions
an arbitrary number of levels. This solution
and solutions are inapplicable in the WSN
relies exclusively on symmetric key schemes, is
regime and would only lead to a waste of scarce
highly distributed, and takes into account node
sensor resources. However, the absence of
interaction patterns that are specific to clustered
reliable transport altogether can seriously impair
WSNs. proposed a solution for securing
event detection. Hence, the WSN paradigm
heterogeneous hierarchical WSNs with arbitrary
necessitates a collective event-to-sink reliability
number of levels. This project provides security
notion rather than the traditional end-to-end
for network setup and reconfiguration, as well as
notion. Reliable transport in WSNs has not been
for the normal network operation traffic. This
studied from this perspective before. The notion
scheme sets up pair wise keys between a cluster
of event-to-sink reliability is necessary for
head and each of its children (or group of
reliable transport of event features in WSNs.
children) using lightweight group key based
This is due to the fact that the sink is only
mechanisms whenever possible, falling back on
interested in the collective information of a
more
number of source nodes and not in individual
whenever necessary.
sensor reports. This is also the reason why
traditional end-to-end reliability notions and
expensive,
BS-mediated
mechanisms
3 Existing System
transport solutions are inappropriate for WSN.
Existing system proposed a suite of
Based on such a collective reliability notion, a
secure time synchronization protocols[2] where
new reliable transport scheme for WSN, the
different
Event-Sink Reliable Transport (ESRT) protocol,
addressed with a protection against pulse delay
is presented in this paper. ESRT is a novel
attacks. However, these protocols require the
transport solution developed to achieve reliable
nodes to go through the phase of key discovery
hop,
group
synchronization
are
with
their
preloaded
themselves.
static
Moreover,
Communicates
with
keys
the
many
among
protocols
messages
increase the communication costs of the network
and making them not applicable for militaryscenarios
communication
where
pattern
a
more
may
be
Time
to
synchronize the sensor Network with security, It
type
4 Problem Formulation
feasible
preferred.
However, the drawback of this work stems from
its statistical nature. In the work by Sun, the
authors propose a secure time synchronization
[2] protocol utilizing Global Positioning System
(GPS) devices starting from source nodes. The
proposed work requires a shared static key
between the communicating nodes and assumes
Wireless
synchronization
Sensor
Networks
protocol
(WSNs)
for
send
separate synchronization messages and uses
static
pair
wise
key-based
cryptographic
mechanisms to ensure that the clocks [10] of
each sensor device are securely globally
synchronized (i.e., every device has the same
clock value). An alternative approach, Secure
sOurce-BAsed loose Synchronization (SOBAS)
protocol is used to securely synchronize the
events in the network, without the transmission
of synchronization control messages.
4.1 Proposed System
that the source nodes will be equipped with GPS
devices, which is more costly due to periodic
An effective technique to securely
communication to GPS satellites and increased
synchronize the data with source and sink node
radio activity increases the opportunity for
in the network has been proposed, without
malicious threats. Also, GPS may not be
transmission
effective for all sensor applications (e.g.,
messages separately. Here proposed system
underwater medium) as explained in the
focus on ensuring that each source node gets
previous section. Additionally similar to, the
synchronized with sink nodes also event
nodes exchange many messages. A secure time
ordering on sink node can be achieved and nodes
synchronization
heterogeneous
along the data delivery path such that event
sensor networks with a novel adoption of
reports is generated by the sink are ordered
Identity-Based Cryptography (IBC) and Pairing-
properly. In SOBAS[9], source and destination
Based Cryptography[6] (PBC) over elliptic
nodes are synchronized loosely, so that the data
curves, but the work did not present any
is delivered accurately. Initially the source node
performance
clock
requests the time based key management module
precision values. Furthermore, two pertinent
to generate the key, when there is a need to
studies based on associating keys with time
transfer data between the source and destination
information available in sensor nodes were
node. Once the source gets the key it requests
presented in papers.
the neighbour nodes to send public key[3]. The
protocol
evaluation
for
to
provide
of
synchronization
control
neighbour node which has the key it replies that
for both WSNs and sensor-based applications
key to source node. Then the source node
where utmost silence is necessary, as SOBAS is
encrypts the data and send to the destination
not chatty.
throw forwarder node. Then the forward node
decrypts the data and checks whether the
5. IMPLEMENTATION
decrypted ID and the given ID is same. If it is
1. Time-based Key Management
same then encrypt the data and sends to the next
2. Implementing Cryptography Techniques
forward node. If it is not same then mark that
3. Performing Filtering-Forward Scheme
data packet as malicious and filters that packet
using dynamic en-route filtering mechanism.
SOBAS uses the full encryption[12] and
5.1 Time-based Key Management
The
Time-based
Key
Management
selective encryption method to encrypt the data.
(TKM)[13] module generates dynamic key by
In full encryption technique each and every
using the local time and initial vector value.
forwarder node do the encryption and decryption
When a source node has data it sends to the sink
process. The Selective encryptions only a certain
due to either an external stimulation by the sink
fraction of the nodes along the path do the
or a self-initiated periodic report, it uses its local
encryption operations. After that the next
clock value as the key.
forwarder node continues the same process until
the packet reaches to the destination node.
Two operational modes:
Cryptography module is used to check whether

Stateless mode
the received data is malicious or not. SOBAS

Stateful mode
provides an effective dynamic en route filtering
mechanism, where the malicious data is filtered
from
the
network.
With
The stateful mode, a receiver sensor can
SOBAS,
have a table for each sender sensor, where
synchronization is achieved at the sink as
individual offset values for each sender is
quickly, as accurately, and as surreptitiously as
recorded. The next time the sensor receives a
possible. Simulation results show that SOBAS is
packet from the same sender, it will have a tick
an energy efficient scheme under normal
window centred on the associated offset value
operation and attack from malicious nodes. In
for this sender. This makes the effort of the
addition to being suitable for the applications
receiver easier when it tries to find the correct
where the centralized decision authority acts on
key for the sender.
the information collected from the network,
SOBAS approach to synchronization with
dynamic en-route filtering[14] is also well suited
In the stateful mode, a sensor also
with the source node along a data delivery path
remembers a previously seen malicious node. It
toward the sink with the Full-re encryption or
doesn’t maintain the tick window table.
Selective-re encryption modes of operation. At
this module, the forwarder node gets the
5.2 Implementing Cryptography Techniques
source’s local clock value from the cryptography
The Cryptography module addresses the
security part of SOBAS. This module obtains the
dynamic
key
from
the
Time-based
module and updates its local clock value
accordingly.
Key
Management (TKM) module and performs the
necessary security service. It is also used to
verify the key from the TKM.
If the key value received from the TKM
module is not correct then a new key is obtained
from the TKM module. This process continues
until the correct key is found or the packet is
marked as malicious to be discarded in the
filtering-forwarding-scheme module when all
attempts to find the correct key are exhausted
within the tick window.
5.3
Performing
Filtering-Forward
Scheme
(FFS)
Finally the filtering-forward scheme
module performs the function as shown in
Figure 1 Cryptography and Forwarding
Filtering Module
Figure 1. The system eliminates the data if the
node failed to produce proper key. The FFS
module filters the incoming packet out of the
6 RESULT ANALYSIS
6.1 Nodes Vs Delay
network if it is classified as a bad packet or
Delay refers, the average time elapsed
malicious packet by the cryptography module or
after a packet is send and before it is received.
otherwise forwards it to the upstream nodes. In
Figure 2 shows, the selective-stateful encryption
SOBAS, this module is also responsible for the
process is well suitable for SOBAS and the
synchronization process of the forwarder node
delay is decreased from 3 to 12 % when
compared with full-stateful encryption, fullstateless
encryption
and
selective-stateless
encryption techniques.
Figure 3 Nodes Vs Transmission Energy
6.3 Nodes Vs Computational Energy
Computational
energy
refers,
linear
dependence of rate and energy. Figure 4 shows,
the selective-stateful encryption process is well
Figure 2 Nodes Vs Delay
suitable for SOBAS and the computational
6.2 Nodes Vs Transmission Energy
energy is decreased from 2 to 12 % when
Transmission energy refers, energy taken
for transmitting the data from source to
destination. Figure 3 shows, the selective-
compared with full-stateful encryption, fullstateless
encryption
and
selective-stateless
encryption techniques.
stateful encryption process is well suitable for
SOBAS
and
the
transmission
energy
is
decreased from 2.5 to 5% percentage when
compared with full-stateful encryption, fullstateless
encryption
and
selective-stateless
encryption techniques.
Figure 4 Nodes Vs Computational Energy
7 CONCLUSION
SOBAS nodes use their local time and
initial vector values as one-time dynamic key to
encrypt each message. In this way, SOBAS
provides an effective dynamic en-route filtering
mechanism, where the malicious data is filtered
from the network. Loose synchronization in
SOBAS, the data are sent to destination as
quickly and accurately as possible. The SOBAS
decreases the number of opportunities for
malicious entities to eavesdrop, intercept packets
by reducing the number of messages exchanged
between the nodes. Thus, energy savings from
the reduced transmission is used for the local
security
computation.
Selective
encryption
approach to encrypt the data in SOBAS is well
suitable to reduce the energy consumption.
Future
work
includes
studying
further
opportunities for increasing the unused key-trial
attempts at a node, and addressing insider
threats.
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