1. WEP Protocol Weaknesses and Vulnerabilities
Riad Lemhachheche
Jumnit Hong

2. OUTLINE Introduction to WEP Problems with WEP Solutions to WEP
802.1x
802.11i
WPA
Conclusion

3. Introduction to WEP
Basically a pseudo random number generator that encrypts data packets.
Start with generic packet
Use a secret key plus IV to seed RC4 stream cipher to create pseudo random number
Create a CRC-32 of data portion of packet which is then called ICV.
Data || ICV XOR Pseudo Random Number = Encrypted portion of WEP Packet

4. Shared before communication begins Created by Sending Device
How WEP Works
Frame Header
Frame Body
FCS
Secret Key
(40Bits)
RC4 Algorithm IV
(24bits)
Generic Packet Frame
Shared before communication begins
Created by Sending Device
Integrity Check Algorithm
ICV
WEP Packet Frame
Encrypted

5. Problems with WEP Key Generation ICV Generation
Weak Key’s and Weak IV’s
WEP Attacks

6. Key Generation Problems
The main problem of WEP is Key Generation.
Secret Key is too small, only 40 Bits.
Very susceptible to brute force attacks.
IV is too small.
Only 16 Million different possibilities for every packet.
Secret Keys are accessible to user, therefore not secret.
Key distribution is done manually.

7. ICV Generation Problems
The ICV is generated from a cyclic redundancy check (CRC-32)
Only a simple arithmetic computation. Can be done easily by anyone.
Not cryptographically secure.
Easy for attacker to change packet and then change ICV to get response from AP.

8. Weak Key’s and IV’s
Certain keys are more susceptible to showing the relationship between plaintext and ciphertext.
There are approx 9000 weak keys out of the 40 bit WEP secret key.
Weak IV will correspond to weak Keys.

9. Attacks Replay 802.11 LLC Encapsulation Denial of Service Attacks
Statistical gathering of certain ciphertext that once sent to server will cause wanted reaction.
LLC Encapsulation
Predictable headers to find ciphertext, plaintext combinations
Denial of Service Attacks
Flooding the 2.4Ghz frequency with noise.

10. Solutions to WEP
802.1x
WPA
802.11i
All much more secure.

11. 802.1x
IEEE 802.1X is a standard from the IEEE for port-based network access control. The 802.1X authentication process for 802.1X applied to WLAN works as follows:
The client access the wireless medium using CSMA/CD and associate with the access point
The access point accepts the association and places the client on hold in an unauthenticated ’holding area’. It sends an authentication request to the client. The access to the LAN for the client is still blocked
The client provides an identification response with a username or some kind of identifier. It is forwarded by the access point to a RADIUS server

12. 802.1x (2)
The RADIUS server looks up the username from a local database or another authentication server.
If the username has been identified by the RADIUS server then the access point starts challenging the client. The way the client is challenged is not specified by the protocol and so depends on the hardware/software implementations. Nevertheless, no secret information, like passwords, are passed over the medium as plaintext.
The client initiates a reverse challenge with the RADIUS server to achieve mutual authentication. This protects the network from rogue access points installed by hackers to obtain client authentication data.
Once the mutual authentication is performed, a virtual port on the access point is opened up and the client can fully access the network.

13. WPA (Wireless Protected Access)
Wi-Fi Protect Access (WPA) has for goal to be an update to WEP weaknesses. It is designed to be:
strong,
Interoperable & security replacement for WEP
software upgradeable for certified Wi-Fi products
available quickly.
To fulfill these goals, 2 major enhancements have been made:
Improved data encryption
User authentication

14. WPA vs. 802.11i WPA and IEEE 802.11i Comparison
WPA will be forward-compatible with the IEEE i security specification.
WPA is a subset of the current i draft, taking already available pieces of the i draft such as its implementation of 802.1x and TKIP.
The main pieces of the i draft that are not included in WPA are :
Secure IBSS & Secure fast handoff,
Secure de-authentication and disassociation,
Enhanced encryption protocols such as AES-CCMP.

15. 802.11i Possibility of two modes to encrypt packets TKIP or CCMP.
TKIP uses current WEP and wraps a new packet around the WEP packet. Used to support legacy devices.
CCMP uses AES in CBC mode to create MAC and encrypt data packets. New encryption standard.

16. 802.11i-CCMP

17. Conclusion
The WEP protocol described in is not sufficient at creating cryptographically secure communication between a wireless client and an access point. It will only stop the casual attacker, with virtually no security to protect a network from the professional hacker.
The problems with WEP are as follows:
Key Generation and Distribution
Weak IV’s and Key’s
Predictable Integrity Check algorithm (CRC-32)
Freely available tools to break WEP

18. Conclusion (2) Solutions
Modifying WEP by utilizing TKIP enables superior security to that of WEP, but the most secure way to provide cryptographically secure communication is to use well known and studied standard encryption algorithms such as AES. CCMP utilizes AES in cipher-clock-chaining mode to produce a MAC and to encrypt the message. This is the most secure way to transfer confidential information wirelessly. Both CCMP and TKIP are in the new i standard.
WEP only protects against casual attackers and the new i will provide much needed wireless protection from malicious users.