Security and Privacy in Body Sensor Networks - E-Healthcare Systems and Wireless Communications - page 119

Table 3. Energy consumption of public-key signature creation and verification on MICA2 sensors (Wan-
der et al., 2005)

Cryptographic
Algorithm

Signature creation
energy consumption
(mJ)

Signature verification
energy consumption
(mJ)

Key exchange
client-side energy
consumption (mJ)

Key exchange
server-side energy
consumption (mJ)

RSA-1024 304 11.9 15.4 304

ECDSA-160 22.82 45.093 22.3 22.3

RSA-2048 2302.7 53.7 57.2 2302.7

ECDSA-224 61.54 121.983 60.4 60.4

and (2) communication energy that results from
transmitting and receiving security-related data
such as key agreement information, MAC values,
and digital signatures. The communication energy
component is much higher than the processing
energy component. Wander et al. (2005) found out,
through real measurements on the Mica2dots sen-
sor platform, that sending 1 byte of data consumes
36 times more energy than processing 1 byte of
data using the famous AES encryption algorithm.
Data reception is found out to be somehow more
efficient than data transmission but still 18 times
more energy demanding than AES encryption
processing. Some sensible energy measurements
for sending, receiving, and processing 1 byte of
data are presented in Table 4.
Based on the above energy measurements,
BSN security protocol designers should pay con-
siderable attention to reducing the communication
requirements of the security functions especially
in the key management phase and in the construc-
tion of the protocol message exchange. For ex-
ample, using smaller-size symmetric-key MACs
or ECC-based signatures instead of larger RSA/
DSA signatures for ensuring data integrity and
authentication aids in reducing the protocol com-
munication energy consumption. Moreover, ap-
plying certain compression and data aggregation
functions plays a role in minimizing the data
transfer size and hence in conserving the sensors
energy if these functions do not interfere with the
monitoring requirements of the BSN application
(some critical BSN applications require prompt,

real time, and accurate data monitoring patterns
that do not accept any form of processing delays
or data manipulation resulting from the application
of compression and aggregation functions).

CONTEXT-AWARE PRIVACY
PRESERVATION IN BSNS

In the sixth section, we described how IBE can aid
in providing a secure access control mechanism
for protecting the patient's private data extracted
by a BSN. The presented IBE scheme is secure in
fulfilling the patient's privacy requirements and
flexible in specifying the access control informa-
tion by associating it with the public encryption
identifier. However, this model requires the patient
to be in a conscious state to provide the private
parameters necessary to decrypt and hence grant
access to the sensitive data. This requirement
cannot be guaranteed in critical and emergency

Table 4. Energy consumption of data transmis-
sion, reception, and processing on MICA2 sensors
(Wander et al., 2005)

Operation Energy consumption

Data transmission 59.2μJ/byte

Data reception 28.6μJ/byte

AES encryption 1.62μJ/byte

SHA-1 hashing 5.9μJ/byte