One possible attack on the
transport layer is the flooding attack. Transport protocols that maintain states
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Chapter 17 A Survey on Sensor Network Security
at either end are vulnerable to the flooding attack which can exhaust memory
in nodes. A powerful adversary (e.g., a laptop) can send many connectionestablishment
requests to a sensor node, and each request causes sensor nodes
to allocate memory to maintain the connection states. A sensor node has
limited memory, and its memory will be exhausted under the flooding attack.
One defense against flooding attack is to limit the number of connections
that a node can request (in a period of time). In [37], the authors propose to
use client puzzles to defend against DoS attack. Considering a client / server
connection scenario, a client needs to demonstrate the commitment of its own
resource to each connection by solving the client puzzles, which are created
and verified by the server. The server distributes the puzzles, and clients
wishing to connect must solve them and present them to the server before
establishing a connection. Thus, the number of connections can be limited by
the available knowledge to solve the puzzles.
3 Security Objectives for Sensor Networks
Wireless sensor networks have many unique features that di?®er from mobile
ad hoc networks and other wireless (and wired) networks. When considering
security in sensor networks, we need to state assumptions on the network.
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