1. 802.1X and AKE Comparison Nancy Cam-Winget, Atheros
November 2001
802.1X and AKE Comparison
Nancy Cam-Winget, Atheros
Russ Housley, RSA Laboratories
Tim Moore, Microsoft
Jesse Walker, Intel
Cam-Winget,Housley,Moore,Walker

2. 802.1X Requirements/Decisions
November 2001
802.1X Requirements/Decisions
Security session Management
802.1X owns the security session, decides when to authenticate, re-authenticate abd deauthenticate
Encryption is offloaded to MAC but encryption decision is made during 802.1X authentication by the authentication server – whether it gives the master key to the authenticator
Liveliness of station/AP via 802.1X authentication or re-associate signature
Race Conditions
Synchronization done by always having a free KeyID
Requires 2 KeyIDs for key mapping keys
Rekey at twice the key lifetime
Roaming and key hand-off
Reuse 802.1X EAPOL-Key message
Key messages must be in clear to allow roaming
Implies that 802.1X must be unencrypted
Fast handoff via IAPP supported
Fast handoff enabled by signature in re-association (562)
WEP “rapid rekeying”
Reuse EAPOL-Key from 802.1X
Authenticator “owns” network so stations must obey key messages
EAPOL-Key is acknowledged from receiver because it is a data message
Authenticator is not told if station cannot obey the message
Cam-Winget,Housley,Moore,Walker

3. AKE Requirements/Decisions
November 2001
AKE Requirements/Decisions
Security session Management
MAC owns the security session, decides when to end session
Encryption performed in MAC and encryption enforced by security association setup completion
Master Key is provided from external source (802.1X, Manual, Whatever…)
No security assumptions of Master Key
Different approaches for key-mapping keys and default keys
Pre-shared key authentication proves liveness
Use management channel message handshakes to
Synchronize transition from old key to new key
simplify interface with ULA
defeats race condition at 802.1X level
Roaming and key hand-off
Master Key is transferred by extranal source (TGf, Whatever…)
Liveness confirmed by security association establishment
WEP “rapid rekeying”
Arbitrary rekey interval, but default keys must be done on published schedule
Cam-Winget,Housley,Moore,Walker

4. Similarities Secure session is required State machine is the same
November 2001
Similarities
Secure session is required
State machine is the same
2 keys are needed for key roll-over
Authenticated exchange used for key roll-over
Roaming facilitated
Implementation complexity roughly the same for the whole system
Implementation will probably in driver or above
Likely to be OS specific
Cam-Winget,Housley,Moore,Walker

5. Differences 802.1X AKE November 2001 Uses in-band messages
MAC layer must bypass encryption for 802.1X traffic identified by ethertype
Secure session resides in 802.1X
Authenticator decides when to rekey: MAC to Application Layer interface needed (MIB?)
Informational not normative
No enforcement of what to do when replay counter is exhausted
IBSS complexity
KeyMap keys are managed by individual peers
Default keys are managed by beacon transmitter
Rekey transition has no confirm
Old key stays live until next new key
Rekey is message based for both keymap and default keys
Liveness algo uses MD5
AKE
Uses out-of-band messages
Secure session resides in MAC
MAC decides when to rekey
IBSS always managed by beacon transmitter
Rekey transition uses confirm
Frees key storage for other purpose
Rekey is message based for keymap keys and countdown for default keys
Liveness algo uses AES
Cam-Winget,Housley,Moore,Walker