Table 1.

Notations.

Symbol	Definition
U	A user
ID	A user’s identity
PW	A user’s password
DID	A user’s dynamic login identity
GW-node	Gateway node of WSN
Sn	Nearest sensor node of WSN
h(.)	A secure one-way hash function
xa	A permanent secret parameter generated securely by the GW-node and stored in some defined sensor nodes before deploying the WSN
K	A symmetric key of GW-node which shared between the GW-node, users and the sensor nodes
||	A string concatenation operation
⊕	A string XOR operation
⇒	A secure channel
→	A public channel