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Secure and Efficient Key Management Protocol (SEKMP)
for Wireless Sensor Networks
Majid Alshammari and Khaled Elleithy
Department of Computer Science and Engineering
University of Bridgeport
Bridgeport, CT 06604
maalsham@my.bridgeport.edu; elleithy@bridgeport.edu
ABSTRACT
Wireless sensor networks (WSNs) are used in the many critical
applications, such as, military, health, and civil applications.
Sometimes such applications require that the WSNs to be
randomly deployed in inaccessible terrains such as a remote
territory. As a result, the sensors are left unattended and become a
potential target for an adversary. Therefore, we propose a highly
Secure and Efficient Key Management Protocol for WSN, called
SEKMP. The proposed protocol (SEKMP) adapts a new key
management approach by leveraging the advantages of
asymmetric cryptography and employs them in a very efficient
way for delivering the session key to sensor nodes.
Categories and Subject Descriptors
E.3 [Data Encryption]: Public key cryptosystems; C.2.1
[Computer-Communication Networks]: Network Architecture and
Design – Wireless communication
Keywords
Wireless sensor networks.
1. INTRODUCTION
Wireless sensor networks (WSN) is a growing area, and today
become involved in variety of applications due to the nature of
sensors nodes that are small in size and cost effective [1]. WSN in
inaccessible terrains is usually left unattended. As a result, they
become an easy target for an adversary. In such environments, the
major security concern of WSN is the key management protocol.
Thus, there are varieties of protocols in literature that utilize one
or more of the following schemes: symmetric, asymmetric, or
quantum cryptography for addressing the security of key
management in WSN. However, the direct application of these
schemes is not the best choice when it comes to limited-resource
environments such as WSN. With this in mind, we came up with a
very Secure and Efficient Key Management Protocol for WSN,
called SEKMP. The proposed protocol (SEKMP) adapts a new
key management approach by inheriting the advantages of
asymmetric cryptography and employs it in very efficient way for
delivering the session key to sensor nodes.
Symmetric-based key management protocols are considered more
resource-efficient than Asymmetric-based key management. The
downsides of these protocols are: 1) maintaining a large number
of keys, 2) or dependency on intermediary nodes for the keys
distribution. For example, [2] and [3]. Asymmetric-based key
management protocols proved to be secure in literature, and thus,
they are one of the best protocols for the key distribution. The
downside is, the direct application of these protocols in WSN
leads to have many keys, and as a result, affecting the protocol
performance. For example, in [4] the sink node must maintain
keys with sensor nodes. Where is the number of nodes.
2. THE PROPOSED PROTOCOL
SEKMP includes three phases: Pre–deployment phase, Key
distribution phase, and Key refreshment phase. Table 1 shows the
notations used in the proposed protocol.
Table 1. Notations
Notation Description
N Number of nodes.
PUS Public key used in the sink node.
PRN Private key used in each node.
KS Session key used to encrypt the communication.
C Ciphertext.
M Plaintext.
EK (X) Function for Encrypting X with K.
DK (X) Function for Decrypting X with K.
2.1 Pre-deployment phase
In pre-deployment phase, a pair of keys, called public (PUS) and
private (PRN) key is generated for the WSN. The public key (PUS)
is assigned to the sink node, whereas, the private key (PRN) is
assigned to the sensor nodes. Afterwards, the sink node has the
public key (PUS), and each sensor of the WSN has a copy of the
private key (PRN). Furthermore, building Wireless Sensor
Network of N nodes requires two keys only, one for the sink node
and the other one for the sensors nodes.
2.2 Key distribution phase
After the sensor nodes have been deployed, the sink node
generates a random session key (KS), and then encrypts the
session key by using its key, the public key (PUS). Then, the sink
node broadcasts the following cipher message C = EPUS (KS) to
its neighbors. These neighbors broadcast the same cipher message
to their neighbors if any, in multi-hop fashion until all sensor
nodes get the cipher message. Since all the sensor nodes already
have the private key (PRN), they can decrypt the cipher message C
= EPUS (KS) as, KS = DPRN(C). In the end, the entire nodes
securely receive the session key (KS). Figure 1 shows the key
distribution phase.
2.3 Key refreshment phase
In the key refreshment phase, the sink node can generate a new
session key (KS) on time-basis (e.g. generating a new session key
every 24 hours), or on event-basis, (e.g. generating a new session
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ANCS’14, October 20–21, 2014, Los Angeles, CA, USA
ACM 978-1-4503-2839-5/14/10.
http://dx.doi.org/10.1145/2658260.2661775
253
key whenever a node detects a specific event) based on the
desired application, and then securely broadcasts it to the all
sensor nodes as it does in the key distribution phase. The key
refreshment phase makes the proposed scheme more secure
because of its flexibility of generating a new session key at any
time and for any reason.
Figure 1. key distribution phase.
3. PROPOSED PROTOCOLS ANALYSIS
3.1 Security analysis
In this section, the security of the proposed protocol (SEKMP) is
analyzed and investigated based on the following security
services: Confidentiality, Integrity, and Authenticity.
3.1.1 Confidentiality
The proposed protocol (SEKMP) assures the confidentiality of the
communication among sensors nodes by using a session key (KS).
This session key is securely delivered by utilizing the asymmetric
encryption properties.
3.1.2 Integrity
The integrity is achieved in the proposed protocol by encrypting
the traffic by the authorized nodes to prevent data modification.
Also, the protocol can employ Message Authentication Codes
(MAC) to guarantee that the message has not been altered.
3.1.3 Authentication
This security service is assured by using a pair of keys, called
public (PUS) and private (PRN) key. Since the sink node is the
only node that has the public (PUS) key, it encrypts the session
key (KS) by the public key and broadcasts it to the sensor nodes.
Once the sensor nodes successfully decrypt it by the private key
(PRN), this authenticates the sink node to the sensor nodes in the
network and proves that the session key (KS) is sent by a trusted
source.
3.2 Performance analysis
In this section the performance of proposed protocol (SEKMP) is
analyzed according to Efficiency, Connectivity, Scalability, and
Flexibility.
3.2.1 Efficiency
The efficiency of the proposed protocol (SEKMP) is achieved by
using a small number of keys compared to other protocols such as
[2], [3], and [4]. It also provides an extremely secure key
management protocol in the same time. As a result, SEKMP
preserves the energy of the sensors. Table 2, represents the
number of keys being used by the sink node/KDC, and each
sensor node in SEKMP, [2], [3], and [4].
Table 2. Numbers of keys
Scheme/protocol. Number of keys in
the sink node.
Number of keys in
each sensor node.
SEKMP 1 1
[2]
√
√
[3] x /2 -1
[4] 2
3.2.2 Connectivity
Connectivity of the proposed protocol is considered high because the
protocol ensures that each node would receive a session key (KS) by
broadcasting an encrypted message contains that session key.
3.2.3 Scalability
The proposed protocol is able to maintain the security of the
wireless sensor as the network expands, and it can be achieved by
adding N nodes with an assigned private key (PRN).
3.2.4 Flexibility
The proposed protocol is flexible due the fact that a node can be
added or removed easily; even the sink node can be replaced
without affecting the security of WSN. For example, a sink node
can be added after it gets assigned with the public key (PUS). Also
with the same approach, a sensor node can be added after it is
assigned with the private key (PRN).
4. CONCLUSIONS
The SEKMP protocol adapts a new key management approach by
leveraging the advantages of asymmetric cryptography properties
and employs them in a very efficient way for delivering the
session key to sensor nodes. We have simulated and compared
SEKMP to existing protocols in literature in terms of the number
of keys being used. Based on the simulation results, SEKMP is
protocol is more efficient than those protocols. Thus, we believe
that adapting SEKMP protocol addresses several security
challenges of the key management in WSNs.
5. REFERENCES
[1] I. F. Akyildiz and M. C. Vuran, Wireless sensor networks vol. 4: John
Wiley & Sons, 2010.
[2] H. Chan and A. Perrig, "PIKE: Peer intermediaries for key establishment
in sensor networks," in INFOCOM 2005. 24th Annual Joint Conference
of the IEEE Computer and Communications Societies, 2005, pp. 524-
535.
[3] L.-C. Wuu, C.-H. Hung, and C.-M. Chang, "Quorum-based key
management scheme in wireless sensor networks," presented at the
Proceedings of the 6th International Conference on Ubiquitous
Information Management and Communication, Kuala Lumpur,
Malaysia, 2012.
[4] Y. Zhang, "The scheme of public key infrastructure for improving
wireless sensor networks security," in Software Engineering and Service
Science (ICSESS), 2012 IEEE 3rd International Conference on, 2012,
pp. 527-530.
PUS
PRN
PRN
PRN
PRN
PRN
PRN
PRN
EPUS (KS)
EPUS (KS)
EPUS (KS)
EPUS (KS)
EPUS (KS)
EPUS (KS)
EPUS (KS)
The Sink node Generates a random session key KS
Broadcasts EPUS (KS)
to all nodes
254
