Among various others, the Grayhole and Blackhole
attacks are considered as the most dangerous attacks towards
adhoc network. Even though, there exist several mechanisms
for securing adhoc networks from such attacks, traditional
preventive approaches in this regard have serious limitations
and several disadvantages. Nodes share a single symmetric
key for encryption and decryption of messages. Also, there is
a problem of group re-keying which is complex and time
consuming task. Also AODV fails to remove malicious nodes
during the route discovery process and therefore does not
succeed to transfer all data packets to the destination under
Blackhole and Grayhole attacks. Most of the traditional
methods lack reliability. Also, under these attacks, the Packet
Delivery Ratio (PDR), Throughput, may decrease, as the
number of malicious nodes increases. So a new mechanism
for securing ad hoc networks has been proposed.
Whenever a network is created using NS-2 simulator, an
advanced version of AODV is applied first to remove the
malicious nodes causing Grayhole and Blackhole attack. Then
the nodes are arranged in a spanning tree topology. Once the
network is created, communication occurs only among
authenticated neighbours. Further RSA key exchange is
applied before encryption and decryption of messages. To
improve security, encryption has been done twice. It ensures
forward and backward secrecy. Whenever the topology
change, the new neighborhood key is calculated and is given
to all authenticated neighbours.
In conclusion, as a result of all these mechanisms,
Grayhole and Blackhole attacks can be prevented and
specifically worthy of attention is the proven increase in
throughput and increased Packet Delivery Ratio.