CS549: Cryptography and Network Security

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1 CS549: Cryptography and Network Security by Xiang-Yang Li Department of Computer Science, IIT Cryptography and Network Security 1

2 Notice This lecture note (Cryptography and Network Security) is prepared by Xiang-Yang Li. This lecture note has benefited from numerous textbooks and online materials. Especially the Cryptography and Network Security 2 nd edition by William Stallings and the Cryptography: Theory and Practice by Douglas Stinson. You may not modify, publish, or sell, reproduce, create derivative works from, distribute, perform, display, or in any way exploit any of the content, in whole or in part, except as otherwise expressly permitted by the author. The author has used his best efforts in preparing this lecture note. The author makes no warranty of any kind, expressed or implied, with regard to the programs, protocols contained in this lecture note. The author shall not be liable in any event for incidental or consequential damages in connection with, or arising out of, the furnishing, performance, or use of these. Cryptography and Network Security 2

You may not modify, publish, or sell, reproduce, create derivative works from, distribute, perform, display, or in any way exploit any of the content, in whole or in part, except as otherwise

3 Cryptography & Network Security Wireless LAN Security Road to i Xiangyang Li Cryptography and Network Security 3

4 Contents Introduction Problem: b Not Secure! Wired Equivalent Privacy WEP Types of Attacks b Proposed Solutions 802.1X Wi-Fi Protected Access (WPA) i: The Solution Conclusion Cryptography and Network Security 4

5 Introduction Popular in offices, homes and public spaces (airport, coffee shop) Most popular: b Example: Yahoo! DSL Wireless Kit Theoretical 11Mbps Operate at 2.4GHz band DSSS/FSSS modulation similar to CDMA phones Cryptography and Network Security 5

DSL Wireless Kit Theoretical max @ 11Mbps Operate at 2.

6 Introduction Standards: IEEE Series b 2.4GHz a 5.7GHz band g 2.4GHz band 802.1X security add-on i high security Cryptography and Network Security 6

7GHz band 802.11g 54Mbps @ 2.4GHz band 802.

7 Problem: b Not Secure! No inherent security Wired Wireless media change was the objective Wired Equivalent Privacy (WEP) The only security built into Uses RC4 Stream Cipher in a bad way Vulnerable to several types of attacks Sometimes not even turned ON Cryptography and Network Security 7

Equivalent Privacy (WEP) The only security built into 802.

8 Wired Equivalent Privacy WEP RC4 stream cipher Designed by Ron Rivest for RSA Security Very simple Initialization Vector (IV) Shared Key The issue is in the way RC4 is used IV (24 bits) reuse and fixed key Early versions used 40-bit key 128-bit mode effectively uses 104 bits Cryptography and Network Security 8

the way RC4 is used IV (24 bits) reuse and fixed key Early versions used

9 Wired Equivalent Privacy WEP RC4 Key Stream Encryption (source: Cryptography and Network Security 9

10 Types of Attacks Attacks Confidentiality Integrity Availability Cryptography and Network Security 10

11 Types of Attacks Attacks on Confidentiality Traffic Analysis Passive Eavesdropping Very easy to do Active Eavesdropping Unauthorized Access Cryptography and Network Security 11

12 Types of Attacks Attacks on Confidentiality and/or Integrity Man-In-The-Middle Attacks on Integrity Session Hijacking Replay Attacks on Availability Denial of Service Cryptography and Network Security 12

Session Hijacking Replay Attacks on Availability

13 802.11b Proposed Solutions Virtual Private Network Closed Network Through the use of SSID Ethernet MAC address control lists Replace RC4 with block cipher Don t reuse IV Automatic Key Assignment Cryptography and Network Security 13

control lists Replace RC4 with block cipher Don t reuse

14 802.1X: Interim Solution Port-based authentication Not specific to wireless networks Authentication servers RADIUS Client authentication EAP Cryptography and Network Security 14

15 802.1X Problems 802.1X still has problems Extensible Authentication Protocol (EAP) One-way authentication Attacks Man-in-Middle Session Hijacking Cryptography and Network Security 15

16 802.1X Proposed Solutions Per-packet authenticity and integrity Lots of overhead Authenticity and integrity of EAPOL messages Two-way authentication Cryptography and Network Security 16

17 Wi-Fi Protected Access (WPA) Addresses issues with WEP Key management TKIP Key expansion Message Integrity Check Software upgrade only Compatible with 802.1X Compatible with i Cryptography and Network Security 17

Check Software upgrade only Compatible with 802.

18 802.11i Finalized: June, 2004 Robust Security Network Wi-Fi Alliance: WPA2 Improvements made Authentication enhanced Key Management created Data Transfer security enhanced Cryptography and Network Security 18

Authentication enhanced Key Management created Data

19 802.11i - Authentication Authentication Server Two-way authentication Prevents man-in-the-middle attacks Master Key (MK) Pairwise Master Key (PMK) Cryptography and Network Security 19

20 802.11i Key Management Key Types Pairwise Transient Key Key Confirmation Key Key Encryption Key Group Transient Key Temporal Key Cryptography and Network Security 20

21 802.11i Key Management Source: Cryptography and Network Security 21

22 802.11i Data Transfer CCMP Long term solution mandatory for i compliance WRAP TKIP Latest AES encryption Requires hardware upgrades Provided for early vendor support Carried over from WPA Cryptography and Network Security 22

23 802.11i Additional Enhancements Pre-authentication Roaming clients Client Validation Password-to-key mappings Random number generation Cryptography and Network Security 23

24 Conclusion Basic b (with WEP) Massive security holes Easily attacked 802.1X Good interim solution Allows use of existing hardware Can still be attacked Cryptography and Network Security 24

25 Conclusion Wi-Fi Protected Access Allows use of existing hardware Compatible with 802.1X Compatible with i i May require hardware upgrades Very secure Nothing is ever guaranteed Cryptography and Network Security 25

CS 356 Lecture 29 Wireless Security. Spring 2013

CS 356 Lecture 29 Wireless Security Spring 2013 Review Chapter 1: Basic Concepts and Terminology Chapter 2: Basic Cryptographic Tools Chapter 3 User Authentication Chapter 4 Access Control Lists Chapter