Cyber Physical Security Solutions for Pervasive Health Monitoring Systems - E-Healthcare Systems and Wireless Communications - page 150

system. We therefore call them Pervasive Health
Monitoring Cyber Physical Systems (PHM-CPS).
The involvement of the physical process intro-
duces interesting possibilities and challenges in
providing security for such systems. The principal
focus of this chapter is the development of new
security approach for PHMS called CYPsec that
leverages their cyber-physical nature. We further
present two security solutions that leverage the
CPS nature of PHMS. However, before that it is
essential to discuss what cyber-physical systems
are and what it takes to secure them. In the rest of
the paper we use the term PHMS and PHM-CPS
interchangeably.

be an enabler of the cyber element by providing:
(1) Sustainability : it can provide a powering source
for the operation of the cyber element in a seam-
less manner, e.g., the human body can provide a
plethora of sources (heat, respiration, locomotion)
to power sensors in a BAN CPS ; (2) Safety : it
can provide adequate protection of the physical
aspects of the cyber element, e.g., growth of tissue
around implants to shield it and the body from
each other; (3) Efficiency : it can provide mecha-
nisms which allow the cyber element to function
more efficiently, e.g., human body can provide a
conduit between sensors in a body area network
by providing a channel for communication which
makes the communication more efficient in terms
of power required and secure (Hachisuka, Takeda,
Terauchi, Sasaki, Hosaka, & Itao, 2005).
Many of the applications that we call CPS
today were not always so. They have evolved over
a period of time to take such a character. A case
in point is a braking system in smart cars. Once
purely physical systems, the breaks have been aug-
mented by cyber elements (improved electronics)
for improved accuracy and precision. Nowadays
braking systems are not designed independent of
the electronics. In fact the physical element does
not exist without the cyber, the requirements of
the control electronics become part of the require-
ments of the break itself. Such development, in
not just automotive, but also other fields such
as biomedical, infrastructure, and utilities have
resulted in integrated blurring the demarcation
line (from a system's perspective) between the
cyber and physical. Therefore, it would be folly
to view them as “computing power enhancing the
environment or physical processes improving the
efficiency of the computing platform” alone. The
combination of the cyber and physical elements, in
a CPS, brings about a more revolutionary change
in the way either works ( i.e., the whole is greater
than the sum of its parts).

BACKGROUND: CYBER-
PHYSICAL SYSTEMS

Cyber-Physical Systems is not just about a physi-
cal element being controlled by a cyber element
or vice-versa. The cyber element is more of an
enabler of the physical element and manifests
itself in many forms, including: (1) Improved ef-
ficiency : the processing and storage provided by
the cyber element can improve the operational
efficiency of the physical process, e.g., the abil-
ity to compute the amount of oxygen in a car
engine allows the engine to ensure the perfect
oxygen to fuel ratio of efficient burn; (2) Problem
detection : the sensing capabilities and processing
capabilities of the cyber element allow for timely
detection and mitigation of any abnormalities in
the operation of the physical process, e.g., detec-
tion of ailments in PHM-CPS; and (3) Emergent
behavior : the computation capability allows the
physical process to provide services which it
could not have provided on its own, e.g., smart
home-grids can practice power usage curtailment
based on context (weather, peak usage times) by
switching off appliances such as sprinklers on a
rainy day. The physical element similarly can also