Cryptography Reference
In-Depth Information
Message size evaluation:
The total message packet size during the transmissions equals | ID j |+| t i |+| m |+| j |+|
h ( m || t i || )|, where | h ( M || t i || )| is a hash value, which is 20 bytes while SHA-1 is used.
| ID j | + | t i | are very small, that is, 2 bytes each, and | m | is assumed to be 20 bytes. The
total message size of a transmission packet is 44 + | j | bytes, whereas | j | is variable.
For example, when using the Tate pairing (Chapter 3), the elliptic curve E is defined
over F p , the order q of G 1 and G 2 is a 160-bit prime. Moreover, p could be a 512-bit
prime to achieve a higher level of security than 1024-bit RSA, and G is a q -order multi-
plicative subgroup of the finite field
F
.
2
p
7.4.2 Cross-Layer Routing
In any communication system, all parties must agree on a set of rules to be used when
exchanging messages. For example, rules could include when messages can be sent and
the language used for sending these messages. Such an agreement in a communication
system is called a protocol . Instead of using a single complex protocol that outlines all
the details for possible communication, early network designers chose to divide the
communication problem into sections and subsections. Furthermore, each section is
designed, developed, and tested separately. The main intention of the designers of the
layered protocol architecture was to facilitate a functional framework, wherein each
layer has a well-defined functional and service definition. Although, this model laid
the foundation to support heterogeneous networked systems, it was more applicable to
legacy wireless (2G and 3G networks) and IP networks. In addition, the legacy net-
works focused on QoS and inter- and intracommunication between different networks.
On the other hand, WSN focuses on the optimal usage of network resources, thereby
increasing the lifespan of the sensor network. It was observed that such a resource-
constraint environment would drastically benefit from a cross-layer design in which
knowledge shared across different layers of the stack would provide a holistic energy-
efficient solution (Shakkottai et al 2003). Akyildiz et al. (2006) proposed one of the
early unified cross-layer protocols, which replaced the entire conventional, layered,
protocol architecture for WSN. This new protocol efficiently combines the informa-
tion and the functionalities of the communication layers into a single energy-efficient
protocol. The design principle is based on “initiative determination,” which embeds
intrinsic communication functionalities that are needed for successful communication
in WSN. The “initiative determination” concept facilitates the freedom for each node
to decide on whether to participate in communication. As a result, the next hop in each
communication is not determined in advance. Cross-layer security is discussed in detail
in Chapter 8.
7.5 Summary
In this chapter, we looked at routing schemes in WSN. We classified routing in WSN
into data centricity, location information, network layering and in-network processing,
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