Vulnerability In Wi-Fi

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 Request for shared key auth. Nonce N E(N, KA-B) Bob (base station) Authentication response Alice

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