They also discuss the impact of di?®erent
keying mechanisms on the e?®ectiveness of in-network processing in sensor
networks. Deng et al. [2] discuss several security mechanisms for supporting
in-network processing in hierarchical sensor networks.
Several interesting key pre-distribution schemes are classified and reviewed
in the following subsections.
Fully Pairwise Key Scheme
In the fully pairwise key scheme, each sensor node has a symmetric key with
each other sensor node, i.e., there are a total of n(n + 1)/2 symmetric keys
called pairwise keys, in the network, where n is the number of sensor nodes
in the network. Each sensor node is preloaded with n ??’ 1 symmetric keys.
In the fully pairwise key scheme, a compromising/captured sensor node
does not reveal other security information except the n ??’ 1 pairwise keys
within itself, where n ??’ 1 = O(n). One drawback of this scheme is that the
scheme requires a large amount of memory storage space for n??’1 symmetric
keys, when n is large. Furthermore, most of the keys may never be used.
??-secure Key Scheme
A trade-o?® between security and memory space in the fully pairwise key
scheme can be parameterized with the ??-secure key scheme introduced in
[18]. The ??-secure property is that if the number of compromising sensor
nodes is smaller than ?? among n sensor nodes, these comprising sensor nodes
reveal no security information about any pairwise key between any two noncompromised
sensor nodes [38, 39].
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