Table 1.

Explanation of notation used in Figure 1.

Symbol	Description
ni, nj, nk, nl	Ordinary nodes in the line topology
Ln	Leader node
{ }k	Symmetric encryption/decryption with key k
M	Transmitted sensor data
ks	Secret encryption source key
kni	Secret encryption adjacent key of node i
ki	Secret encryption individual key of node i
kLn	Secret encryption leader node key
{{M}ks}kni	Sensor data encrypted with source and adjacent keys
{M}ki	Message encrypted with individual key of node i
{M}kLn	Message encrypted with leader nod key