TKIP Michael MIC problems


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TKIP Michael MIC problems

Postby Fernando Enriquez » Sat, 02 Jul 2005 06:27:51 GMT

Hi everyone:

We've set up a complex installation for one client based on 40 Cisco 
1200 & 1100 APs working as parent-repeater (we have some branches with 
parent-repeater-repeater). We've deployed LEAP on APs and clients both. 
Everything is working fine until any client changes from one AP to 
another. When it starts to transmit traffic it gets blocked because of 
MIC encryption error. The situation remains for a few minutes, when 
suddenly encryption works again.

To minimize impact we have enables key-rotation every 20 seconds but the 
problem remains and users aro not able to work properly.

To validate users we have installed freeradius with leap support. Radius 
log shows that authentication is working fine (no errors)

This is a log excerpt of what happens when client 0040.96a7.c594 
desassociates from AP and associates to AP

Re: TKIP Michael MIC problems

Postby Uli Link » Sat, 02 Jul 2005 17:50:48 GMT

Fernando Enriquez schrieb:

It's a feature to block a station after a number of MIC failures.
But this should not happen with allowed, legitimate stations.

What's the fw and driver version of your clients?

For the 350 series the very first fw supporting WPA with TKIP was 5.30.17.

What's the config of your APs? What's the IOS version on you APs?
The 350 series does not work with cipher set to TKIP+WEP (migration mode)

Tip: set up one low traffic AP as WDS, this will allow fast secure roaming.
For 350 clients I prefer CCKM over WPA, you can allow both on a SSID.


Re: TKIP Michael MIC problems

Postby Fernando Enriquez » Wed, 06 Jul 2005 00:15:49 GMT

I updated FW on clients and APs both to latest versiones a couple of
weeks ago but problem persists.

Cipher is pure TKIP, not migration mode.

I will try WDS to see if using this the roaming gets smoother. I will
tell you.

Thanks a lot for your interest

Similar Threads:

1.TKIP MIC failures


Ive got a few AP1200's that Ive just deployed. Most only have 1 or 2
associations right now as Im ramping it up for production.

Ive got 1 client an IBM laptop with an Intel 2200BG card that keeps
causing these errors on the AP.

%DOT11-4-TKIP_MIC_FAILURE_REPORT: Received TKIP Michael MIC failure
report from the station 000e.3568.a238 on the packet (TSC=0x0)
encrypted and protected by pairwise key.

I see these 1 every few minutes, sometimes it will happen more often
and then the radio interface is put on hold and all my WPA clients are
disassociated. All WPA clients diassociated is bad.

%DOT11-3-TKIP_MIC_FAILURE_REPEATED: Two TKIP Michael MIC failures were
detected within 0 seconds on Dot11Radio0 interface. The interface will
be put on MIC failure hold state for next 60 seconds.

So I read some about these messages and they point to someone attackign
my AP but these are being generated by MAC Addrs that are friendly.

Heres the rundown on my setup,  Cisco AP1200's IOS 12.3(2)JA configed
for WPA \TKIP  with a MS IAS RADIUS server backend.

Anyone ever see these errors before ?  Thanks


2.WPA/TKIP with AP1200

Hi gurus

I'm trying to configure an Windows XP SP1 supplicant with Patch Q815485 
with my laptop HP Nx7010. Initially I work with EAP-TLS + WPA TKIP & 
AP1200, it seems to work fine but after a few seconds the connection is 
broken and supplicant doesn't reconnect with the AP.
HAve you found this issue ?

Can you help me?



3.Cisco ACS 3.3 and Windows 2003 IAS using EAP-TLS and TKIP

I was wondering has anyone every setup using Cisco ACS 3.3 (Radius)
with Windows 2003 IAS to authenicate with PKI cards for wireless and if
so what sets should I follow.  TIA

4.TKIP vs Broadcast Key Rotation

In some of the Cisco documentation, they state that broadcast key rotation
(BKR) "is an excellent alternative to TKIP if your wireless LAN supports
wireless client devices that are not Cisco devices or that cannot be
upgraded to the latest firmware for Cisco client devices."

I don't really understand how this is true. If BKR is only rotating the keys
for broadcast frames, then the user's session (unicast) key isn't touched
by this mechanism, right? So, the classic WEP cracking vulnerabilities
still apply, right?

Must be something I'm missing here... who can enlighten me?


5.Security of Cisco TKIP implementation on older products

I am still using Cisco AIR-352 with 12.3(8) IOS as access point, to provide 
connectivity on my wlan ad 802.11b speeds, with WPA-PSK TKIP security.

I have on a site, two AIR-BR352 point to point links at about 4km.
The bridges BR350 uses Wep128 security, and I know that it is unsecure.
On the config pages, I have enable MIC and TKIP settings.

So in the end I have these options enabled:
WEP 128

This is the extract from cisco's documentations about the two options.

# Message Integrity Check (MIC) -- MIC is an additional WEP security feature 
that prevents attacks on encrypted packets called bit-flip attacks. The MIC, 
implemented on both the access point and all associated client devices, adds 
a few bytes to each packet to make the packets tamperproof.

# Temporal Key Integrity Protocol (TKIP) -- TKIP, also known as WEP key 
hashing, is an additional WEP security feature that defends against an 
attack on WEP in which the intruder uses an unencrypted segment called the 
initialization vector (IV) in encrypted packets to calculate the WEP key.

In the end, these bridges are in WEP128, but are they vulnerable to the 
common wep flaws (IV vector, and vulnerable to airsnort's scans)  ?

To be secure, I use a GRE+IPSEC (at the moment using DES encryption, later I 
will use AES128) tunnel between the two sites connected via the wifi 
bridge, to be more secure.


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