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Analysis of Wired Equivalent Privacy (WEP) Implementation in Wireless LANs

This analysis explores the Wired Equivalent Privacy (WEP) protocol used for wireless LANs, covering its working mechanism, vulnerabilities such as IV collisions and checksum modifications, and recommendations for improvement. The overview includes the introduction, mechanisms, attackable entries, improvements in WEP implementation, and conclusions with recommendations for enhanced security measures.

murphy-williams
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Analysis of Wired Equivalent Privacy (WEP) Implementation in Wireless LANs

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  1. ANALYSIS OF WIRED EQUIVALENT PRIVACY CS265, Spring 2003 Xunyan Yang

  2. OVERVIEW • Introduction • Working Mechanism • Attackable Entries • Improvement In WEP Implementation • Conclusion & Recommendations

  3. INTRODUCTION • What is WEP --- Wired Equivalent Privacy • What is WEP used for --- Provides confidentiality for wireless LAN • What’s problems with WEP --- Cryptographic errors

  4. WORKING MECHANISM A string cipher using the RC4 encryption algorithm • A message (plaintext M) • A Integrity Check (checksum algorithm c ) • A shared secret key (short key k ) • A per packet Initialization Vector (IV) Ciphertext = (M·c(M)) XOR RC4(IV ·k)

  5. WORKING MECHANISM(Contd.) Integrity Check • 32-bit Cyclic Redundancy Check (CRC-32) checksum Confidentiality • Initialization Vector (IV) A 24-bit field and appended to the cleartext part of a message

  6. ATTACKABLE ENTRIES • IV Collisions • IV Reuse • Modify Checksum

  7. IV COLLISION & REUSE • IV will be exhausted after about five hours 1500-byte packet at the speed of 11MbPS: 1500 * 8 / (11 * 10^6) / 60^2 * 2^24 • A common wireless card resets the IV to 0 each time a card is initialized, and increments the IV by 1 with each packet.

  8. MODIFY CHECKSUM • CRC-32 is a linear algorithm • Compute the bit difference of two CRCs based on the bit difference of the messages • Flip arbitrary bits in an encrypted message and correctly adjust the checksum

  9. IMPROVEMENT IN WEP IMPLEMENTATION Automatic WEP rotation • Constant automatic key rotation • Continual key replacement • Unique key generation http://www.wavelink.com

  10. CONCLUSTION & RECOMMENDATION WEP Provides Inadequate Security • Assume that the link layer offers no security • Don’t rely on WEP. Use higher-level security mechanisms • Place all access points outside the firewall • Assume that anyone within physical range can communicate on the network as a valid user • Always turn on WEP in your access point

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