www.ijecs.in
International Journal Of Engineering And Computer Science ISSN:2319-7242
Volume 4 Issue 2 February 2015, Page No. 10346-10350
An Efficient Pairwise Key Establishment Scheme for
Wireless
Sensor Networks
Using ORP
#1
*2
#3
Gisha N , Jeena Sara George ,Sushitha Susan Joseph
Final b-tech students#1,*2,Assistant Professor #3
Department of Computer Science and Engineering
Mar Baselious College Christian of Engineering Technology,Peermade,Kerala,India
1
gishanandan@gmail.com
sarageorgektm@gmail.com
3
sushisusan64@gmail.com
2
Abstract- Wireless sensor network has many application such as environment sensing, building safety
monitoring, earthquake prediction etc. Security is critical issue in sensor networks. A fundamental security
service is to establish pairwise key shared between two sensor nodes, which is basis of other security such as
encryption and authentication. The prime problem in key management is to establish secure keys between the
sensor nodes. To avoid this pairwise key establishment is used. This scheme consists of two key pools. One key
pool is hashed value of keys in another key pool. With the one-way hash function, this scheme can make
attackers get less key information from the compromised sensor nodes. Along with this Otway Rees protocol is
used to provide integrity and authenticity. If direct path between two sensors are not present, then by using this
protocol it is easy to find key with the help of intermediate node.
Keywords-Wireless Sensor Network;
Key Management;Otway Rees Protocol;
I.INTRODUCTION
Wireless sensor networks (WSNs) have been widely
deployed for various applications, such as environment
sensing, building safety monitoring, earthquake
prediction etc. WSNs may be deployed in hostile
environments, especially in military applications.
Security is critical issue when sensor networks are
deployed such situations. A fundamental security
service is to establish pairwise key shared between two
sensor nodes, which is the basis of other security such
as encryption and authentication. The prime problem
in key management is to establish the secure keys
between the sensor nodes. However due to
the resource constraints, implementation an efficient
key establishment mechanism is not a trivial task.
Wireless Sensor network consists of large number of
sensors. Each sensor collects the data and sends it to
the neighbour. Security in WSNs is critical. To provide
security data encryption is used. For this key is needed.
Each sensor encrypts the data using the key and send
to the neighbours. Neighbour can decrypt the data
using same the key. So to provide security key
establishment is important. In normal case there exist
only one key for a network. But if any attacker capture
the key, then they get all the data from several sensors
because there is only one key. In order to avoid this
pairwise key establishment scheme is used.
In pairwise key establishment scheme there exist a key
between two sensor. So that if any attacker capture this
key no other sensor node can compromised using that
key. So this scheme provides more security. This
scheme consists of two key pools. One key pool is the
hashed value of keys in another key pool. Because of
the one-way property of the hash function, given the
keys in the first key pool, anybody can compute the
corresponding keys in the second key pool on the fly,
but given the keys in the second key pool, nobody can
compute the corresponding keys in the first key pool.
Pairwise key establishment scheme consist of three
phases. They are Setup phase, Direct key
establishment phase, Path key establishment phase.
Before deploying each sensor node distribute some key
to them. The set phase is performed to initialize the
sensor nodes by distributing keys to them. Key is from
these two key pools either it may from the original key
pool or from the hashed key pool. After being
deployed, if two sensor nodes need to establish a
pairwise key, they first attempt to do so through direct
key establishment. If they can successfully
establishment a common key, there is no need to start
Gisha N#1 IJECS Volume 4 Issue 2 February, 2015 Page No.10346-10350
Page 10346
path key establishment. Otherwise, these sensor nodes
start path key establishment, trying to establishment a
pairwise with the help of other sensor nodes.
The scheme is based on EG scheme and use one-way
hash function to generate a new key pool from a given
key pool. With the one-way hash function, this scheme
can make attackers get less key information from the
compromised sensor nodes. Along with this Otway
Rees protocol is used to provide integrity and
authenticity. If there is a direct path between two
sensors then exchange the key between these two
sensors. If direct path between two sensors are not
present then identify the sensor which has link to the
both source sensor and destination sensor. With the
help of this intermediate node new key is generated
and distributed to the source and destination sensor.
During that time it is difficult to find which sensor has
link between source and destination. If any attacker is
present that act as the intermediate node. To avoid this
Otway Rees protocol is used. By using this, it is easy
to find the intermediate node that has link to source as
well as the destination. This help to identify the
authenticity of the sensor node.
While sending the data between two sensors if any
attacker is present then they corrupts the key
exchanged between source and destination. Normally
it is difficult to identify this. With the help of Otway
Rees protocol it is easy to find whether correct key is
exchanged between two sensors. So pairwise key
establishment scheme helps to establish the key
between two sensors and Otway Rees protocol helps to
provide integrity and authenticity.
II.RELATED WORK
2.1. EG Basic Scheme
Based on key pre-distribution schemes, a random key
pre-distribution was proposed by Eschenauer and
Gligor [2]. It generates a large pool of random keys
and each sensor node is
preconfigured a random subset of keys from a large
key pool before deployment of the network. By doing
this, any two sensor nodes have a certain probability to
share one key. To agree on a pairwise key for
communication, two nodes find one common key
within their subsets and use this key as their pairwise
key. This scheme consists of three phases: key predistribution, shared-key discovery, and path-key
establishment. In the key pre-distribution phase, a
large key pool S is generated first. Then, each sensor
randomly selects m distinct keys from the key pool S,
and stores them in its memory. This set of m keys is
called the sensor’s key ring. After the sensor nodes
have been deployed, the key-setup phase will be
performed. During this phase, each pair of
neighbouring sensor nodes attempts to find a common
key that they share. Since all the keys are randomly
selected from the same key pool, two sensor nodes
may have some overlapped keys in their memories. If
such a key exists, the key will be used to secure the
communication link between these two sensor nodes.
After the key-setup phase is complete, a connected
graph of secure links is formed. Sensor nodes can then
set up path keys with their neighbours with which they
do not share keys. If the graph is connected, a path can
always be found from a source sensor to any of its
neighbours. The source sensor can then generate a path
key and send it securely via the path to the target
sensor. The disadvantage of the EG scheme is that all
pre-load keys are selected from the same key pool. As
the number of compromised sensor nodes increases,
the fraction of the affected keys increases quickly. As a
result, a small number of compromised nodes may
affect large fraction of the secure link.
2.2 Random Key Pre-Distribution Scheme
Chan, Perrig and Song [3] proposed a random key
predistribution scheme for key distribution. It requires
that two sensor nodes share at least q ( q>1) keys
instead of just one common key to establish a secure
connection . The q-composite scheme increase the
network resilience against node captures, but it is only
advantageous when there is few captured sensor nodes.
This scheme also have disadvantage, i.e. large number
of key is needed and also it can be used when the
number of sensor node is less.
2.3polynomial Based Key Distribution
Liu and Li.[4] proposed a similar pairwise key scheme
based on the basic scheme in[3] and based on that
Blundo,Santis and Herzberg proposed a polynomialbased key distribution scheme[5], in which every
sensor node is preloaded with coefficients of a
symmetric bivariate polynomial evaluated at one of its
variables using its identification value and the
symmetry property of a polynomial allows every
sensor node to establish a pairwise key with every
neighbour sensor node or any node in the network
evaluated at their ID value.
In these key pre-distribution schemes, as the number of
number of compromised nodes increases, the fraction
of affected pairwise keys increase quickly. As a result,
a small number of compromised nodes may affect a
large fraction of pairwise. To avoid this problem,
pairwise key establishment scheme is used. There are
two key pools in our scheme and the keys in the first
key pool are generated directly by the setup sever, and
the keys in the second one are the hash value of the
keys in the first key pool. Because of the one way
property of the hash function, given the keys in the
first key pool, anyone can compute the corresponding
keys in the second key pool on the fly, but given the
keys in the second key pool, no one can get the
corresponding keys in the first key pool.
III.PROPOSED SYSTEM
3.1 System Model
Gisha N#1 IJECS Volume 4 Issue 2 February, 2015 Page No.10346-10350
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Sensor
Base Station
Link between sensors
Figure 3.1: Network model
Network model consists of large number of sensor
node. Each sensor senses the data and sends this to
neighbours. Through different sensors this sensed data
is send to the base station. Data is not directly send, it
sends as encrypted form in order to prevent from
attackers. In order to perform encryption a key needed.
To establish a key between two sensors, Pairewise key
establishment scheme is used.
3.2 Key Predistribution Phase
This phase is conducted offline by a setup server
before all sensor nodes have been deployed in a target
field. The purpose of this phase is to assign key
materials to each sensor node. Based on these key
materials, neighboring nodes could setup pairwise keys
after deployment. It has the following steps:
Step 1: The setup server generates w keys, which are
called original keys. Then, the setup sever generates w
new keys, which are called derived keys, by applying a
keyed hash algorithm to the original. These 2w keys
form a key pool P. Here, each key in the key pool has
a two of credentials (Id, T). And T indicates the types
of key. T is 0 or 1. When T is 0, the key is an original
key and when T is 0 the key is a derived key.
Step 2: For each sensor node, the setup server stores
the hash function H, which uses to generate the
derivative keys, into the each sensor node.
Step 3: For each sensor node, the setup server
randomly chooses t original keys and t derivative keys,
which have distinct Id, from the key pool P and stores
them into each sensor node. Here, we call the set of the
t keys the node’s key ring.
3.3 Shared Key Discovery Phase
After the sensor nodes have been deployed, the shared
keys discover phase will be performed. During this
phase, the sensor nodes first perform key discovery to
find out with which of their neighbors the share a key.
To discovery whether a node has a common key ID
with its neighbors, the source node disclose a list of
key IDs and the type these keys to the destination
node. Assume sensor node u and sensor node v are
neighbors. When senor node u is to find or calculate
the shared key with sensor node v, it needs to matches
the key index Id. If the index Id of the key ku in sensor
node u is the same as that of the key kv in sensor node
v. They can compute the pairwise secret key as
follows. There are three cases need to be considered:
Case 1: The T of the key ku is the same as that of the
kv. In this case, the two sensor node can use the ku or
kv as their communication key.
Case 2: The T of the key ku is 1 and that of key kv is 0.
In these case, the sensor node v need to calculate H(kv)
as the pairwise key and sensor node u needs no
calculation and uses kv as the pairwise key. It is
obviously that ku equals to H(kv) .
Case 3: The T of the key ku is 0 and that of key kv is 1.
In these case, the sensor node u need to calculate H(ku)
as the pairwise key and sensor node v needs no
calculation and uses ku as the pairwise key
3.4 Path Key Establishment Phase
If direct key establishment fails, two sensor nodes will
have to start to establishment a pairwise key with the
help of other sensor nodes. To establish a pairwise key
with sensor node u, a sensor node v needs to find a
path between them such that any two adjacent sensor
nodes in the path can establish a pairwise key directly.
Then either sensor node u or v initiates a request to
establish a pairwise key with the other sensor node
through the intermediate nodes along the path.
3.5 Otway Rees Protocol
When there is no direct path, then use intermediate
node for the key establishment. But if any attacker is
present then they corrupts the key exchanged between
source and destination. Normally it is difficult to
identify this. With the help of Otway Rees
protocol(ORP) it is easy to find whether correct key is
exchanged between two sensors.
When sensor1 needs to communicate with sensor3,
there is no direct path. So sensor2 act as the
intermediate
node.
Sensor1
send
(source,
destination,R) to sensor3. Along that (source,
destination, R, RA) which is encrypted using KA is send.
At sensor3 it can see (source, destination, R) and add
RB i.e (source, destination, R, RB) which is encrypted
using KB. This is send to sensor2. Sensor2 know KA
and KB. So this can decrypt it. Sensor2 select one key
RAB for communication between sensor1 and sensor3.
This key is encrypted using KA and KB. Sensor2 sends
(RA, RAB) which is encrypted using KA and (RB, RAB)
which is encrypted using KB to sensor3. Sensor3
decrypt (RB, RAB) using KB and send (RA, RAB) to
sensor1 which is decrypted using KA. By this Sensor1
and sensor3 get RAB as the key and then using that key
they exchange another key which is used as the key
between sensor1 and sensor3.
Gisha N#1 IJECS Volume 4 Issue 2 February, 2015 Page No.10346-10350
Page 10348
sensor which has link to the both source sensor and
destination sensor. With the help of this intermediate
node new key is generated and distributed to the
source and destination sensor. Otway Rees Protocol is
used to find the intermediate node that has link to
source as well as the destination. This help to identify
the authenticity of the sensor node.
V.FUTURE WORK
Pairwise key establishment using Otway Rees protocol
takes more time for finding the key between two
sensors. So this problem is avoided by using enhanced
version of Otway Rees protocol. Also this provides
more security. If any attack on sensor node occurs it
can be easily identified using this protocol. By using
this, a key is established between source and
destination when there is no direct path exists.
Enhanced Otway Rees protocol provides authenticity
and integrity. Thus by using this, it is easy to find
whether correct key is used or not.
Figure 3.4:Otway rees protocol
REFERENCE
By checking R , RA ,RB value we can know that any
attacker is present or not. If any change to the value
occurs then attacker is present otherwise sensors are
secure. In the presence of attacker value of R , RA ,RB
value is not same.The working of Otway Rees Protocol
can be seen from the below figure. Alice represents
sensor1. Bob represent sensor3 and KDC represent
sensor2.
IV.CONCLUSION
Wireless sensor networks (WSNs) have been widely
used for various applications, such as environment
sensing, building safety monitoring, earthquake
prediction etc. Security is critical issue when sensor
networks are deployed such situations. A fundamental
security service is to establish pairwise key shared
between two sensor nodes, which is the basis of other
security such as encryption and authentication. The
prime problem in key management is to establish the
secure keys between the sensor nodes. To provide
security key establishment is important. For that
pairwise key establishment scheme is used. This
scheme consists of two key pools. One key pool is the
hashed value of keys in another key pool. Because of
the one-way property of the hash function, given the
keys in the first key pool, anybody can compute the
corresponding keys in the second key pool on the fly,
but given the keys in the second key pool, nobody can
compute the corresponding keys in the first key pool.
Pairwise key establishment scheme consist of three
phases. They are Setup phase, Direct key
establishment phase, Path key establishment phase.
Along with this Otway Rees protocol is used to
provide integrity and authenticity. If direct path
between two sensors are not present then identify the
[1] I.F. Akyildiz, W. Su, Y. Sankarasubramanian. A
survey on wireless sensor networks. IEEE
Communication Magazine, 2002, 38(8): 102~114
[2] L. Eschenaure and V.D. Gligor, “A keymanagement scheme for distributed sensor networks”.
in: Proc. of the 9the ACM Conference on Computer
and Communications, Washington DC, USA, pp.4147, Nov. 2002
[3] J.Zhang, Q.Cui, X.Liu. An Efficient Key
Management Scheme for Wireless Sensor Networks in
Hostile Environments. in: International Conference on
Multimedia Information Networking and Security,
2009, Hubei, pp.417-420, Nov.2009
[4] H. Chan, A. Perrig and D. Song, “Random key
predistribution schemes for sensor networks”, in: Proc.
20003 IEEE Symposiumon Security and Privacy,
pp.197-313, May 2003
[5] D. Liu, P. Ning, and R. Li, “Establishing pairwise
keys in distributed sensor networks”. ACM
Transactions on Information and System Security,
vol.8, pp.41-77, Feb. 2005
[6] C. Blundo, A. D. Santis, A. Herzberg. S. Jutten, U.
Vaccaro, and M. Yung. “Perfectly secure key
distribution for dynamicconference”, Information and
Computation, vol.1, pp.1-23 , Jan.1995
BIOGRAPHIES
Gisha N#1 IJECS Volume 4 Issue 2 February, 2015 Page No.10346-10350
Page 10349
Jeena Sara George pursuing B-tech- CSE in MBCCET
college of engineering ,Peermade,Kerala, India. She is
interested in Networks,Security.
Gisha N pursuing B-tech-CSE in MBCCET college
ofengineering ,Peermade,Kerala, India. She is
interested in networks,DBMS.
Sushitha
Susan
Joseph (M.E.,2012,
Anna
University,Chennai; B.Tech.,2009, Mahatma Gandhi
University,Kottayam) is an assistant professor in the
Department of Computer Science and Engineering,
MBCCET, Peermade,Kerala. Her main research
interests focus on artificial intelligence, data
mining,wireless sensor networks and data privacy.
Gisha N#1 IJECS Volume 4 Issue 2 February, 2015 Page No.10346-10350
Page 10350