Wide-spread deployment of sensor networks is on the
horizon. Networks of thousands of sensors may present
an economical solution to some of our challenging problems :
real-time traffic monitoring , building safety monitoring
( structural , fire , and physical security monitoring ), military
sensing and tracking , distributed measurement of seismic
activity , real-time pollution monitoring , wildlife monitoring ,
wildfire tracking, etc. Many applications are dependent
on the secure operation of a sensor network , and have
serious consequences if the network is compromised or disrupted.

In sensor network security , an important challenge is
the design of protocols to bootstrap the establishment of
a secure communications infrastructure from a collection
of sensor nodes which may have been pre-initialized with
some secret information but have had no prior direct contact
with each other . We refer to this problem as the bootstrapping
problem . A bootstrapping protocol must not only
enable a newly deployed sensor network to initiate a secure
infrastructure , but it must also allow nodes deployed at a
later time to join the network securely. The difficulty of
the bootstrapping problem stems from the numerous limitations
of sensor networks . We discuss these limitations in
detail in Section 2.2; some of the more important ones include
the inability to utilize existing public key cryptosystems
( since the expensive computations involved could expose
the power-constrained nodes to a denial-of-service attack ),
the inability to pre-determine which nodes will be
neighbors after deployment, and the inability of any node
to put absolute trust in its neighbor ( since the nodes are not
tamper resistant and are vulnerable to physical capture ).