1. M. Kassab, A. Belghith, J. Bonnin, S. Sassi
Fast Pre-Authentication Based on Proactive Key Distribution for Infrastructure Networks
M. Kassab, A. Belghith, J. Bonnin, S. Sassi
ACM WMuNeP`05
2006/10/31
CS Div. NS Lab.
Junbeom Hur

2. Authentication Server
Problem Definition
How to reduce the re-authentication latency during handoff in IEEE network environment?
Authentication Server AP
Authentication
Re-authentication
Station

3. Fig. 1. IEEE 802.1x Architecture
High-speed wireless Internet connectivity
Lack of mobility support
802.1x full authentication per handoff : 1000ms
802.11i recommendation – EAP/TLS
Obstacle for real-time applications (e.g., 50ms of VoIP)
Fig. 1. IEEE 802.1x Architecture

4. EAP/TLS Authentication
PMK = PRF(MK, ‘client EAP encryption’|ClientHello.random|ServerHello.random)
PTK = PRF(PMK, ANonce, SNonce, STAmac, APmac)
Fig. 2. Complete EAP/TLS Authentication Exchange

5. Proactive Key Distribution [Arunesh04]
Fast handoff
Pre-authenticate to the neighbor APs before handoff
Fig. 3. Authentication Exchange Process with PKD
PMK0 = PRF(MK, ‘client EAP encryption’|ClientHello.random|ServerHello.random)
PMKn = PRF(MK, PMKn-1|Apmac|STAmac)

6. Proposed Method PKD with IAPP caching
PKD with anticipated 4-way handshake

7. PKD with IAPP Caching PKD + IAPP cache mechanism
Temporary authentication within a time limit
(a) Pre-authentication
(b) Re-authentication
Fig. 4. Authentication Exchange Process with ‘PKD with IAPP Caching’
PTKx = PRF(PMK, PTKinit|Apmac|STAmac)

8. PKD with Anticipated 4-Way Handshake
4-way handshake through the current AP
(a) Pre-authentication
(b) Re-authentication
Fig. 5. Authentication Exchange Process with ‘PKD with anticipated 4-way handshake’

9. Analysis
m : # of neighbor APs

10. Performance Evaluation
Test-bed
Two STAs associate with an AP
500kb UDP packets with exponential inter-packet time
(a) Re-authentication latency
(b) Association latency

11. Discussion PKD with IAPP caching PKD with anticipated 4-way handshake
Computation overhead
Violation of i security requirements
Mutual authentication and fresh key derivation at each AP
No man-in-the-middle attack
Security degradation from temporary authentication
PKD with anticipated 4-way handshake
Communication overhead
2 X (4-way handshake) per neighbor AP
Unnecessary PTKs computation
Impracticality
No support for f

12. Conclusion Two methods for PKD-based fast pre-authentication
PKD with IAPP caching
Temporary authentication
Security degradation
PKD with anticipated 4-way handshake
4-way handshake during pre-authentication phase
Communication / computation overhead