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sor node was compromised. This is due to the fact
that the body sensors are only loaded by public
parameters that are not sufficient to construct the
private encryption key. The interested reader is
referred to (Tan et al., 2008) for a comprehensive
security analysis.
main criteria to be considered in the security
protocol design are: (1) the choice of employing
public-key or private-key cryptographic primitives
or a combination of both, and (2) managing the
wireless data transmission and reception proto-
col operations due to their significant impact on
energy consumption compared to data processing
operations.
SECURITY-ENERGY
TRADEOFFS IN BSNS
Symmetric-Key vs. Public-Key
Cryptographic Algorithms
As stated earlier in this chapter, BSNs have strict
processing and energy limitations which makes
the design of cryptographic security solutions
really complex and challenging in these environ-
ments. The energy limitations are perhaps the
most critical in BSNs due to the battery-operated
nature of body sensors which makes the possibil-
ity of recharging the battery sources infeasible
when the sensors are embedded inside the human
body. This accessibility issue requires the design
of energy-aware security protocols that aim at
extending the network life span for protracted
periods of time without changing the batteries.
A central goal to be achieved when designing
energy-efficient security protocols for BSNs is
to establish a balance between the security level
provided and the energy consumption incurred.
Any successful security enforcement mechanism
should securely guarantee the health application
security requirements from data confidentiality,
privacy, integrity, authenticity, etc. while keeping
in mind the processing and energy limitations of
body sensor nodes by employing energy-efficient
algorithmic techniques, cryptographic data struc-
tures, and data communication models.
In this section we study the tradeoff between
cryptographic security strength and energy
consumption in BSNs by analyzing the energy
demands of several symmetric and asymmetric
cryptographic primitives on real sensor platforms.
This analysis aids in the selection of suitable
cryptographic algorithms when designing the
components of the BSN security protocols. The
Considering the security requirements and power
limitations of a BSN, the first design choice in
an energy-aware BSN security framework is the
selection of the cryptographic algorithms that
provide the suitable balance between security
strength and energy consumption. Two approaches
are basically followed: using symmetric-key
cryptographic techniques which provide high
performance and thus low energy expenditure
or utilizing public-key cryptographic algorithms
which support better security services mainly in
the fields of key management and digital signa-
tures. Undoubtedly symmetric-key algorithms are
considerably much more efficient in terms of CPU
processing and energy consumption compared
to public-key algorithms. Public-key algorithms
mainly implement resource-intensive opera-
tions on large integers which makes their energy
demands unacceptable on resource-constrained
body sensors. However, the relatively new ECC
public-key cryptosystem discussed in the second
section presents a public-key cryptosystem that
has better performance and energy demands
on resource-limited sensor nodes compared to
traditional asymmetric cryptosystems such as
RSA. Although the energy requirements of ECC
algorithms are still much higher than symmetric-
key ciphering algorithms, it is considered, by
many researchers, a suitable choice for carrying
out key management and signature operations on
more capable body sensor nodes. This fact is sup-
ported by the several cryptographic libraries that
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