28-09-2012, 10:48 AM
Secure Key Exchange and Encryption Mechanism for Ad Hoc Networks
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Abstract
Secured communication in ad hoc wireless
networks is primarily important, because the
communication signals are openly available as they
propagate through air. The lack of any central
coordination and shared wireless medium makes
them more vulnerable to attacks than wired
networks. As nodes in ad hoc network join or leave
dynamically, the efficient key management and
encryption mechanism is required to assure
confidentiality, integrity and authentication of
application data. The objective of this paper is to
propose a key exchange and encryption mechanism
where nodes are organized in spanning tree fashion
and exchange of key occurs only with authenticated
neighbors in ad hoc networks. The proposed method
aims to use the MAC address as an additional
parameter to encrypt as the message specific key to
forward data among the nodes.
INTRODUCTION
Ad hoc wireless networks are defined
as the category of wireless networks that utilize
multi-hop radio relaying and are capable of
operating without the support of any fixed
infrastructure and nodes communicate directly
between one another over wireless channels
[5]. As the wireless channels are openly
available and propagate through the air,
security in ad hoc networks is of primary
concern [4]. In an ad hoc wireless network, the
routing and resource management are done in a
distributed manner in which all nodes
coordinate to enable communication among
them.
KEY EXCHANGE AND
ENCRYPTION TECHNIQUES
Active attacks involve actions
performed by adversaries, for instance the
replication, modification and deletion of
exchanged data. External attacks are typically
active attacks that are targeted to cause
congestion, propagate incorrect routing
information, prevent services from working
properly or shut down them completely.
External attacks can typically be prevented by
using standard security mechanisms such as
firewalls and encryption techniques. To secure
group communication, nodes share a single
symmetric key for encrypting and decrypting
messages in existing systems. In the traditional
group key exchange mechanism, if a new node
joins or leaves then the group key must be
globally updated and distributed among the
nodes in the group. This is referred to as group
re-keying [1,6].
RESULTS AND DISCUSSIONS
As the nodes are organized in spanning tree
topology in this security scheme, the nodes exchange
keys and data only with authenticated neighbors.
This avoids expensive global re-keying operations
when the membership in the network changes or
when the network is partitioned. Fig 5. is a
simulation output of wireless nodes plotted on
NAM in which the packets are transferred
between the nodes involved in the spanning tree
path.
Fig 6. and Fig 7. represent the simulation
outputs of the throughputs of the sending and
receiving packets. The other advantage of this
security scheme is that since encryption is done twice
with two different encryption schemes more security
is imposed. It ensures backward secrecy (a new
member of network cannot access data transmitted
before the member joined) and forward secrecy (a
member cannot access the data that is transmitted
after the member is left)[1]. Whenever the topology
changes with the inclusion or exclusion of a member,
new neighborhood key is computed and is distributed
to all authenticated neighbors.
CONCLUSION & FUTURE ENHANCEMENTS
A novel security scheme in ad hoc networks
is presented which can address the security issues
such as authentication, confidentiality and key
management that would avoid global re-keying. The
proposed scheme which aims at sender deniable
encryption can be widely applicable for voting and
auction protocols. This shall be applicable wherever
group communications is to be established in a
secured manner in an ad hoc environment.