Analysis of wired equivalent privacy
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ANALYSIS OF WIRED EQUIVALENT PRIVACY. CS265, Spring 2003 Xunyan Yang. OVERVIEW. Introduction Working Mechanism Attackable Entries Improvement In WEP Implementation Conclusion & Recommendations. INTRODUCTION. What is WEP --- Wired Equivalent Privacy What is WEP used for

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ANALYSIS OF WIRED EQUIVALENT PRIVACY

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Analysis of wired equivalent privacy

ANALYSIS OF WIRED EQUIVALENT PRIVACY

CS265, Spring 2003

Xunyan Yang


Overview

OVERVIEW

  • Introduction

  • Working Mechanism

  • Attackable Entries

  • Improvement In WEP Implementation

  • Conclusion & Recommendations


Introduction

INTRODUCTION

  • What is WEP

    --- Wired Equivalent Privacy

  • What is WEP used for

    --- Provides confidentiality for wireless LAN

  • What’s problems with WEP

    --- Cryptographic errors


Working mechanism

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)


Working mechanism contd

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


Attackable entries

ATTACKABLE ENTRIES

  • IV Collisions

  • IV Reuse

  • Modify Checksum


Iv collision reuse

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.


Modify checksum

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


Improvement in wep implementation

IMPROVEMENT IN WEP IMPLEMENTATION

Automatic WEP rotation

  • Constant automatic key rotation

  • Continual key replacement

  • Unique key generation

    http://www.wavelink.com


Conclustion recommendation

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


Analysis of wired equivalent privacy

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