1. Vulnerability In Wi-Fi By Angus U CS 265 Section 2 Instructor: Mark Stamp

2. Outline  Why Wireless?  Overview Security in Wirelss Networking  WEP  Authentication  Integrity  Encryptions  Off Standard: Access Control List  Attacks  Future Solution

3. Wireless?  Wire: Limited by power and LAN cable  Mobility  unwire  Laptop & Wireless  Simple Installation  Convenience to use  Cost of equipment  Popularity

4. Wireless Standards  IEEE 802.11b  11Mbps 2.4Ghz band Unlicensed, 1999  IEEE 802.11a  54Mbps, 5Ghz band Licensed  IEEE 802.11g  54Mbps 2.4Ghz band Unlicensed, 2003  IEEE 802.11i: (Amendment)

5. Overview Wireless  Wi-Fi : Wireless Fidelity  Hotspot: Where you can have Wi-Fi access  Two types of Wireless Networking  ad hoc: meeting or conference (no internet)  Infrastructure: base station & clients  Connect to external Network (Internet)  Needs: Access point and/or Wireless NIC

6. Overview Security in Wireless Protocol: WEP Authentication (challenge & Response) Integrity: CRC-32 Encryption: Stream cipher, RC4, with IV

7. WEP  Wired Equivalent Privacy Protocol  Security behind the Wi-Fi  Designed to encrypt and decrypt data for Wi-Fi  Disable or 40 bit keys or 104 bit keys  Uses RC4 encryption algorithm  64 bits for RC4 keys or none  40 bits for WEP key & 24 bits for IV

8. Authentication in WEP  Open & Shared Key  Picture from Mark Stamp  Problem: Know Plaintext Attack Nonce N E(N, K A-B ) Request for shared key auth. Authentication response Alice Bob (base station)

9. Access Control List (not in WEP)  Created by Vendors, not in 802.11 Family  Identity Problem: Who you are?  Based on the shared Key?  Only one shared Key  Access List: a list of MAC addresses  Failure: MAC addresses can be modifiable  Open source device drivers

10. Encryption in WEP  IV + Secret Key XOR Plaintext  IV is only 24 bits, too short  40 bits for WEP is still too short  Remember: The other 64 bits for RC4  Given P1 = P2 then C1 = C2  No session Key, One key for all operations  Encryption and Decryption  Access point & Users

11. Integrity in WEP  No protect against replays  (No sequence Number in Packet)  CRC-32 checksum is not good enough for integrity in experiment  High Possibility of Collision

12. Key Management in WEP  No key distribution systems   Static Key and the same key for everything  Manually Enter the secret key in Both sides  Not practice, is often ignored

13. Attacks in WEP  Numerous Attacks since 2001  Fluhrer-Mantin-Shamir (FMS) attacks  Publicly Released the tools to attack WEP  Off-the-Shelf Hardware and Software  Impossible to detect  Only a couple of hours

14. Solution: IEEE 802.11i  A Future Standard for Wi-Fi  IEEE 802.11i still Amendment  Two new Protocols to address above issues  New key management: IEEE802.1X  Short Term Solution: TKIP  Long Term Solution: CCMP

15. TKIP  Temporal Key Integrity Protocol  No new hardware required but  firmware upgrade & driver upgrade  Three element:  A message integrity code  A packet sequencing  A per-packet key mixing function  128-bit Encryption, 64-bit Authentication

16. CCMP  Counter-Mode-CBC-MAC Protocol  New Protocol in 802.11i  required new hardware  Many properties similar to TKIP  Free from constraints of existed Hardware  RC4 replaced by AES  AES 128-bit, 48-bit IV, no per-packet key  Fix all well known WEP flaws

17. The End  Good-bye