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of the physiological signals at the same time. Last
but not least, human identification key agreement
should operate on physiological body signals with
high degrees of randomness and time variability
to prevent key guessing brute force attacks and to
ensure the freshness of the derived session keys.
In resource-lucrative BSN environments,
energy-capable sensor nodes can rely on public-key
cryptography to agree on a symmetric ciphering key.
Currently ECC-based algorithms are considered the
most efficient public-key cryptographic algorithms
due to several reasons that are discussed in the
second section. The ECDH protocol is the standard
ECC key agreement mechanism that is based on
the Diffie-Hellman key exchange. In spite of the
security and management advantages provided
by the application of public-key cryptographic
algorithms and protocols in securing BSNs, these
techniques continue to be very resource demand-
ing and not feasible except on highly energy- and
processing-capable body sensor nodes.
Data Confidentiality and Integrity Protocols:
The security of the confidentiality and integrity
protocols relies mainly on successfully executing a
secure key agreement and distribution mechanism.
Once the symmetric session keys are securely
available in the address space of the sensor nodes,
these keys can be fed to standard encryption and
MAC algorithms to achieve the required confiden-
tiality and integrity properties of the exchanged
messages as discussed in the fifth section. Using
public-key algorithms, even ECC-based, for do-
ing the encryption operations is highly expensive
and not really considered an option for providing
message confidentiality in BSN environments. In
the same sense, using public-key digital signatures
on individual messages for supporting data integ-
rity and non-repudiation security services is too
compute- and energy-intensive. In BSN environ-
ments, ECC-based digital signatures are usually
applied on a group of messages to amortize the
computational cost over that group.
Privacy Preservation and Access Control:
The design of privacy-preservation and access
control protocols depends mainly on two main
properties: (1) the energy and processing capa-
bilities of the nodes forming the BSN and (2) the
patients' health situations that should be handled
by the privacy-preserving scheme. The IBE-lite
protocol discussed in the sixth section provides
an efficient and flexible access control scheme
making it a suitable choice for operation on low-
end body sensor nodes. However IBE-lite was
not designed to handle emergency and life-critical
patient situations and health conditions and thus
the need arises for policy-based and context-
aware access control systems that can manage
the different patient health situations. Such kind
of systems is discussed in the eighth section. The
main limitation in these context-aware privacy
preservation and access control schemes is their
elevated energy requirements which make them
only feasible on high-end body sensor nodes.
CONCLUSION
In this chapter, we presented a comprehensive
survey of the state of the art research in the field
of BSN security and privacy. The chapter started
by pointing out the security challenges faced by
today's BSN implementations and the implications
these challenges have on the safety and privacy of
the human subject. After this introduction, a brief
background on ECC and IBE was presented to
familiarize the reader with the general concepts of
these cryptosystems that are widely used in current
wireless sensor security protocols. Afterwards, the
chapter discussed some popular key agreement
protocols based on human identification and the
data confidentiality and integrity protocols that
build on top of these key agreement schemes.
Next, the chapter presented an IBE-based BSN
Privacy-Preserving Protocol for protecting the
privacy of the patient's data by employing effi-
cient access control constructs. The chapter then
focused on two main challenges that are highly
crucial in the BSN security and privacy context:
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