1. Robust Security Network (RSN) Service of IEEE 802.11
December 2002
doc.: IEEE /794r0
December 2002
Robust Security Network (RSN) Service of IEEE
Shen Ping
Southeast University
Nanjing China,
Shen Ping, Southeast University, China
shen ping, Southeast University, China

2. RSN Security Feature ESS network architecture
December 2002
doc.: IEEE /794r0
December 2002
RSN Security Feature
ESS network architecture
Access Control (AC) in DS supports 802.1x authenticator
802.1x authenticated key management protocol
Authentication Server (AS) in DS provide authentication service
Secure capabilities negotiation, including ciphersuite and authenticated key management suite
Mutual authentication and certificate, e.g. EAP-TLS
Enhanced data protection mechanisms, such as TKIP, WRAP and CCMP
Protection of management and control frames
Pre-authentication of the BSS-transition STA
Shen Ping, Southeast University, China
shen ping, Southeast University, China

3. December 2002
RSN architecture
Shen Ping, Southeast University, China

4. 802.11 Security Services Station Service (SS)
December 2002
doc.: IEEE /794r0
December 2002
Security Services
Station Service (SS)
Privacy
WEP mechanism
Authentication
Open system authentication
Shared key authentication
Deauthentication
Pre-authentication
Distribution System Service (DSS)
Association/Disassociation/Reassociation
Shen Ping, Southeast University, China
shen ping, Southeast University, China

5. Relationships between service
December 2002
Relationships between service
Shen Ping, Southeast University, China

6. Class 1 frame Control frames Management frames Data frames
December 2002
Class 1 frame
Control frames
Management frames
Probe request/response
Beacon
Authentication
Deauthentication
ATIM
Data frames
Data frame with FC bit “To DS” and “From DS” both false
Shen Ping, Southeast University, China

7. December 2002
RSN Service
RSN service provide 802.1x authenticated key management protocol between STA and AC.
RSN service is neither a SS nor a DSS.
RSN service on STA is a SS
RSN service on AC is a DSS
STA supports 802.1x supplicant, and AC supports 802.1x authenticator.
Shen Ping, Southeast University, China

8. Cipher suite negotiation
December 2002
Cipher suite negotiation
The state diagram is unchanged from the 1999 specification. STA and AP must use IEEE open system authentication. RSN IE is added to authentication frame to negotiate the cipher suite between STA and AP.
RSN IE in first frame of open system authentication provide a cipher suite list of STA. The cipher suite list shows all cipher suite supported by STA.
AP must support all cipher suites. AP selects the highest one of the STA cipher suite list for unicast. The multicast cipher must always be the lowest unicast cipher enabled. The result is sent in RSN IE of final frame.
Shen Ping, Southeast University, China

9. 802.1x authenticated key management protocol
December 2002
802.1x authenticated key management protocol
802.1x authenticated key management protocol is provided by RSN service between STA and AC.
802.1x message packets are encapsulated in data frame of class 1 frames.
All 802.1x message packets pass by AP.
AC sends the PTK and GTK to AP over a secure channel between them, e.g. IPsec.
Shen Ping, Southeast University, China

10. 4 way handshake protocol
December 2002
PMK
RADIUS
Generate PMK between STA and AS
802.1x authentication protocol
Final frame (RSN IE)
First frame (RSN IE)
Open system authentication
STA AP AC AS
Generate PTK and GTK between STA and AC
4 way handshake protocol
PTK、GTK
IPSec
Control frames, management frames and data frames
802.11
Phase 1
Phase 2
Phase 3
Shen Ping, Southeast University, China

11. Three phases of State 1 Phase 1 Phase 2 Phase 3
December 2002
Three phases of State 1
Phase 1
Using open system authentication frames to negotiate cipher suite
Phase 2
Using 802.1x authentication protocol to generate PMK between STA and AS
AS sends PMK to AC over the secure channel of RADIUS
Phase 3
Using 4 way handshake and group key update to generate PTK and GTK for the STA
AC configures PTK and GTK to cipher engine of AP for privacy service over the secure channel of IPsec
Shen Ping, Southeast University, China

12. RSN security protocol stack
December 2002
RSN security protocol stack
STA AP AC AS
Transport Layer
TCP/
UDP
TCP/
UDP
EAP
EAP
RADIUS
RADIUS
Network
Layer IP IP
IPSec
IPSec IP IP IP IP
Link
Layer
EAPOL
802.11
802.3
EAPOL
802.3
802.3
802.1X
802.1X
802.11
802.3
Supplicant
Authenticator AS
Shen Ping, Southeast University, China

13. Pre-authentication AC stores the keys of each enabled STA
December 2002
Pre-authentication
AC stores the keys of each enabled STA
Before STA moves from AP1 to AP2 in a ESS, AC configures keys to cipher engine of AP2, and removes keys from AP1
Pre-authentication may not impact the speed with which STA can reassociate between AP2.
Pre-authentication is simple and secure.
Shen Ping, Southeast University, China

14. December 2002
Support of non-RSN STA
The non-RSN station support pre-shared key over 802.1x (only 4-way handshake)
No phase 2 of state 1
The non-RSN station does not support 802.1x supplicant (WEP STA)
No phase 2 and 3 of state 1
Shen Ping, Southeast University, China

15. Negotiation of authenticated key management suite
December 2002
Negotiation of authenticated key management suite
Authenticated key management suite need not be negotiated.
AC can select authenticated key management suite by the type of 802.1x message for different phases. If the first 802.1x message belongs phase 2, unspecified authentication over 802.1x is enabled. If the first 802.1x message belongs phase 3, pre-shared key over 802.1x is enabled.
WEP STA can not send the data frames of class 1 which encapsulate 802.1x message packets.
Shen Ping, Southeast University, China

16. Advantage (1) The 802.11 state diagram is unchanged.
December 2002
Advantage (1)
The state diagram is unchanged.
AP is changed a little.
Authentication service of AP is unchanged.
The new cipher engines of TKIP, WRAP and CCMP added to privacy service of AP.
AP need transmit the 802.1x data frame of class 1 to AC in DS.
Realize the protection of management frames and control frames.
Pre-authentication service is simple and secure.
Shen Ping, Southeast University, China

17. Advantage (2) Negotiation of cipher suite is simple and valid.
December 2002
Advantage (2)
Negotiation of cipher suite is simple and valid.
Authenticated key management suite need not negotiated.
Support non-RSN STA simply.
Compatible 802.1x protocol between wireless and wired LAN.
Saving capital of ESS network
A little change of AP
Only one AC in a ESS
Several ESSs shared one AS
Shen Ping, Southeast University, China

18. Thanks Tim Moore, Microsoft
December 2002
Thanks
Tim Moore, Microsoft
“Suggested Changes to Robust Security Network (RSN) for IEEE ”
Bernard Aboba, Microsoft
“IEEE 802.1x Pre-Authentication”
Shen Ping, Southeast University, China