1. Key agreement in wireless sensor network
Authors: Min-Shiang Hwang and Yung-Chih Lu

2. Introduction Connectivity ratio Resiliency Overhead Rekeying
Authentication
Blind signature

3. Group polynomial-based scheme (1/3)
Theorem
Setup server randomly generates a symmetric multivariate t- degree polynomial
Example:
It’s a symmetric multivariate 3-degree polynomial

4. Group polynomial-based scheme (2/3)
Key agreement
Step1: computes
1: H-sensor’s ID 2: Lu-sensor’s ID
3: Lv-sensor’s ID
Step2: The Setup server loads the sensor node with coefficients
Setup Server
(Base Staton)
distribution
:Lu-sensor
:H-sensor
:Lv-sensor
L-sensor: Low-end sensor s: Step H-sensor: Cluster head

5. Group polynomial-based scheme (3/3)
Key agreement
Step3: Each sensor node broadcasts its own ID
Step4: Receivers use ID to compute a shared secret conference key
K=f(1,2,3)=f(1,3,2)=f(2,1,3)=f(2,3,1)=f(3,1,2)=f(3,2,1)=1387
:H-sensor
:Lu-sensor
:Lv-sensor
L-sensor: Low-end sensor s: Step H-sensor: Cluster head

6. Group polynomial-based scheme2 (1/3)

7. Group polynomial-based scheme2 (2/3)
Symmetric Polynomial Generation Phase
:H-sensor
:Lu-sensor
:Lv-sensor