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

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

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

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

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

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

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

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)

Access Control List (not in WEP)  Created by Vendors, not in 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

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

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

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

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

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

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

CCMP  Counter-Mode-CBC-MAC Protocol  New Protocol in i  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

The End  Good-bye