1. The dangers of pre-shared key and why a certificate OID is needed.
September 2003
The dangers of pre-shared key and why a certificate OID is needed.
Arunesh Mishra, Minho Shin, William Arbaugh
University of Maryland
College Park
Insun Lee, Kyunghun Jang
Samsung Electronics
Mishra, Shin, Arbaugh, Lee, Jang

2. September 2003
Pre-shared key (PSK)
Everyone shares the same PMK therefore we have both an active and a passive attack by insiders.
Mishra, Shin, Arbaugh, Lee, Jang

3. Passive Attack - Eavesdropping
September 2003
Passive Attack - Eavesdropping
An insider (defined by knowledge of the PSK) can capture the 4-way handshake and derive the PTK allowing them to intercept traffic passively.
Mishra, Shin, Arbaugh, Lee, Jang

4. Active Attack - Man in the middle
September 2003
Active Attack - Man in the middle
An insider can establish a man in the middle (MiTM) easily.
Mishra, Shin, Arbaugh, Lee, Jang

5. This should not be new to you
September 2003
This should not be new to you
But- what is interesting is that the same problems exist with the use of certificates, if they are not created properly, i.e. How does the STA know the presented certificate belongs to a AAA server?
There is no DNS or IP connectivity to verify the certificates attributes as in TLS.
Mishra, Shin, Arbaugh, Lee, Jang

6. September 2003
Enter the OID
MSFT caught this previously in L2TP, fortunately, and carried the prevention technique over to EAP/TLS.
XP requires both a server and client OID in certificates:
Server:
Client:
STA ONLY accepts a server certificate with the proper OID (Assumes CA only issues OID to AAA servers).
Mishra, Shin, Arbaugh, Lee, Jang

7. September 2003
Recommendation
Add informational text to draft explaining the dangers of PSK and strongly suggesting the use of both a server and client OID.
Seek approval by the appropriate body of the server and client OIDs.
Mishra, Shin, Arbaugh, Lee, Jang

8. September 2003
Straw Poll
Would you approve of informational text that explains the dangers of PSK and strongly suggesting the use of both the server and client OIDS?
If the group is in favor, text will be provided by Thursday morning for a vote in the afternoon.
Mishra, Shin, Arbaugh, Lee, Jang