Cryptography Reference
In-Depth Information
overhead of transmission by establishing pairwise keys. In SecLEACH, for example,
nodes that do not share a pairwise key with others in its preloaded key ring cannot
participate in any cluster and have to elect themselves as cluster heads. Such a problem
is called the orphan node problem, and this problem increases the overhead of trans-
mission. As an evolution of the traditional certificate-based cryptography, ID-based
cryptography (IBC) is receiving high regard since its invention (Section 4.3). The main
idea is to derive an entity's public key from its identity information (email address, SIP
URI, or any biometric information). Recently, the concept of IBC has been increas-
ingly considered in WSN environments (Chapters 5 and 6). In the next section, we
look at routing protocols in WSN and the applicability of IBC in WSN routing.
7.3.1 Routing Protocols in WSN
Routing in ad-hoc networks has been very challenging due to node mobility. Hence, a
routing path established in the beginning between the source and the destination may
not exist at a later time interval. Furthermore, in a resource-constraint environment
such as WSN, the energy levels of the intermediate nodes must be considered in mak-
ing routing decisions.
Routing protocols in WSN can be broadly classified into proactive, reactive, hybrid,
and location-aware routing protocols (Xiao et al. 2007). In a proactive routing scheme,
each node maintains an up-to-date routing table by frequently querying its immediate
neighbors for routing information. An example of such a scheme is the Destination
Sequenced Distance Vector (DSDV) routing protocol (Perkins and Bhagwat 1994).
However, one of the major drawbacks with such schemes is the additional overhead
due to frequent routing updates. In contrast, reactive routing involves on-the-fly route
establishment and is demand driven. It is based on a request-response model. The
initial discovery phase, to find the destined node, could involve flooding, and the
response phase establishes the transient active routing path. Examples include Ad-hoc
On-Demand Distance Vector (AODV) routing and Dynamic Source Routing (DSR)
(Perkins and Royer 1999; Johnson and Maltz 1996).
Various hybrid protocols use the node-discovery method of the proactive routing
protocol, along with the on-the-fly routing-path establishment method to produce a
hybrid version of the protocol. Zone Routing Protocol (ZRP) is an example of such
a hybrid scheme (Haas and Pearlman 2001). In position-aware routing protocols, the
nodes select the geographically closest neighboring node when making routing deci-
sions. An example of such a protocol is the Geographic and Energy-Aware Routing
(GEAR) protocol (Yu et al. 2001). However, GEAR does not take security into consid-
eration. Most of the security schemes in WSN have focused on symmetric-key cryp-
tography, due to the notion that asymmetric-key cryptography (RSA-based algorithms)
was computationally intensive. However, symmetric-key cryptography has major draw-
backs with regard to key management, and the security is based upon preshared secret
keys. With the successful implementation of pairing-based cryptographic algorithms
in WSN, a new platform is provided to implement asymmetric-key cryptographic
schemes in WSN (Aranha et al. 2010).
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