Researchers at Carleton
University [12] have extended this approach to control access amongst
BlueTooth wireless devices with future plans of including 802.11 transceivers.
To implement this technology in a wireless sensor network, special equipment
for processing RF signals would be required to overlay the coverage area of the
sensor network. The cost of new equipment can become prohibitive especially
for widespread sensors within a network. Also the deployment of specialized
RF equipment is impractical in a sensor network. This was not of significant
concern to the cellular industry because cellular towers are permanent fixed
infrastructure that provide a monitoring and management point. Additionally,
each tower services thousands of subscribers dissipating the cost of the
equipment.
2.2 Host Fingerprinting
Kohno et al. [11] demonstrate a method for remotely fingerprinting a physical
device by exploiting the implementation of the TCP protocol stack. When the
TCP timestamp option is enabled, outgoing TCP packets reveal information
about the sender??™s internal clock. The authors??™ technique exploits microscopic
deviations in the clock skews to derive a clock cycle pattern as the identity
for a device. For machines that do not enable the timestamp option by default,
such as those running Windows 2000 and Windows XP, this approach
becomes an active one. An active fingerprinting technique is needed to initiate
a connection and trick the fingerprintee into using the timestamp option.
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