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Chapter 6

Chapter 6. IP Security. Henric Johnson Blekinge Institute of Technology, Sweden http://www.its.bth.se/staff/hjo/ henric.johnson@bth.se Revised by Andrew Yang. Outline. Internetworking and Internet Protocols (Appendix 6A) IP Security Overview IP Security Architecture

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Chapter 6

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  1. Chapter 6 IP Security Henric Johnson Blekinge Institute of Technology, Sweden http://www.its.bth.se/staff/hjo/ henric.johnson@bth.se Revised by Andrew Yang

  2. Outline • Internetworking and Internet Protocols (Appendix 6A) • IP Security Overview • IP Security Architecture • Authentication Header • Encapsulating Security Payload • Combinations of Security Associations • Key Management

  3. TCP/IP Example

  4. IPv4 Header

  5. IPv6 Header

  6. IP Security Overview • IPSec is not a single protocol. • Instead, IPSec provides a set of security algorithms plus a general framework that allows a pair of communicating entities to use whichever algorithms to provide security appropriate for the communication.

  7. IP Security Overview • Applications of IPSec • Secure branch office connectivity over the Internet • Secure remote access over the Internet • Establsihing extranet and intranet connectivity with partners • Enhancing electronic commerce security

  8. IP Security Scenario

  9. IP Security Overview • Benefits of IPSec • Transparent to applications (below transport layer (TCP, UDP) • Provide security for individual users • IPSec for route/router security: • A router or neighbor advertisement comes from an authorized router • A redirect message comes from the router to which the initial packet was sent • A routing update is not forged

  10. IP Security Architecture • IPSec documents: • RFC 2401: Security Architecture for the Internet Protocol. S. Kent, R. Atkinson. November 1998. (An overview of security architecture) • RFC 2402: IP Authentication Header. S. Kent, R. Atkinson. November 1998. (Description of a packet encryption extension to IPv4 and IPv6) • RFC 2406: IP Encapsulating Security Payload (ESP). S. Kent, R. Atkinson. November 1998. (Description of a packet emcryption extension to IPv4 and IPv6) • RFC 2408: Internet Security Association and Key Management Protocol (ISAKMP). D. Maughan, M. Schertler, M. Schneider, J. Turner. November 1998. (Specification of key managament capabilities)

  11. IPSec Document Overview

  12. IPSec Services • Access Control • Integrity • Connectionless integrity (aka. data integrity) • Rejection of replayed packets (a form of partial sequence integrity) • Data origin authentication (aka. origin integrity) • Confidentiality • Data confidentiality (encryption) • Limited traffic flow confidentiallity (to prevent traffic analysis) • Refer to http://www.linuxexposed.com/Articles/General/The-longest-short-IP-Sec-Paper.html

  13. Security Associations (SA) • A one way relationsship between a sender and a receiver. • Identified by three parameters: • Security Parameter Index (SPI) • IP Destination address • Security Protocol Identifier

  14. Before applying AH

  15. Transport Mode (AH Authentication)

  16. Tunnel Mode (AH Authentication)

  17. Authentication Header • Provides support for data integrity and authentication (MAC code) of IP packets. • Guards against replay attacks.

  18. End-to-end versus End-to-Intermediate Authentication

  19. Encapsulating Security Payload • ESP provides confidentiality services

  20. Encryption and Authentication Algorithms • Encryption: • Three-key triple DES • RC5 • IDEA • Three-key triple IDEA • CAST • Blowfish • Authentication: • HMAC-MD5-96 • HMAC-SHA-1-96

  21. ESP Encryption and Authentication

  22. ESP Encryption and Authentication

  23. Combinations of Security Associations

  24. Combinations of Security Associations

  25. Combinations of Security Associations

  26. Combinations of Security Associations

  27. Key Management • Two types: • Manual • Automated • Oakley Key Determination Protocol • Internet Security Association and Key Management Protocol (ISAKMP) • RFCs: • RFC2412The OAKLEY Key Determination Protocol. H. Orman. November 1998. (INFORMATIONAL) • RFC2409The Internet Key Exchange (IKE). D. Harkins, D. Carrel. November 1998 (PROPOSED STANDARD) • RFC2408Internet Security Association and Key Management Protocol (ISAKMP). D. Maughan, M. Schertler, M. Schneider, J. Turner. November 1998 (PROPOSED STANDARD)

  28. Oakley • Three authentication methods: • Digital signatures • Public-key encryption • Symmetric-key encryption

  29. All payloads bvegin with the same generic payload header. The ‘Next Payload’ field has a value of 0 if this is the last payload in the mesg. Otherwise it contains the type of the next payload. ISAKMP

  30. ISAKMP Payload Types

  31. ISAKMP Exchange Types • ISAKMP provides a fraework fo rmessage exchange, with the payload types as the building blocks.Five default exchange types should be supported.Note: SA in the table refers to SA type of payload with associated Protocol (Proposal?) and Transform payloads.

  32. Recommended Reading • Comer, D. Internetworking with TCP/IP, Volume I: Principles, Protocols and Architecture. Prentic Hall, 1995 • Stevens, W. TCP/IP Illustrated, Volume 1: The Protocols. Addison-Wesley, 1994

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