Chapter 6

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Chapter 6

  1. 1. Chapter 6 IP Security Henric JohnsonBlekinge Institute of Technology, Sweden http://www.its.bth.se/staff/hjo/ henric.johnson@bth.se Henric Johnson 1
  2. 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 Henric Johnson 2
  3. 3. TCP/IP Example Henric Johnson 3
  4. 4. IPv4 Header Henric Johnson 4
  5. 5. IPv6 Header Henric Johnson 5
  6. 6. IP Security OverviewIPSec is not a single protocol.Instead, IPSec provides a set ofsecurity algorithms plus a generalframework that allows a pair ofcommunicating entities to usewhichever algorithms provide securityappropriate for the communication. Henric Johnson 6
  7. 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 Henric Johnson 7
  8. 8. IP Security Scenario Henric Johnson 8
  9. 9. IP Security Overview• Benefits of IPSec – Transparent to applications (below transport layer (TCP, UDP) – Provide security for individual users• IPSec can assure that: – 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 Henric Johnson 9
  10. 10. IP Security Architecture• IPSec documents: – RFC 2401: An overview of security architecture – RFC 2402: Description of a packet encryption extension to IPv4 and IPv6 – RFC 2406: Description of a packet emcryption extension to IPv4 and IPv6 – RFC 2408: Specification of key managament capabilities Henric Johnson 10
  11. 11. IPSec Document Overview Henric Johnson 11
  12. 12. IPSec Services• Access Control• Connectionless integrity• Data origin authentication• Rejection of replayed packets• Confidentiality (encryption)• Limited traffic flow confidentiallity Henric Johnson 12
  13. 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 Henric Johnson 13
  14. 14. Transport Mode Tunnel Mode SA SA Authenticates IP payload Authenticates entireAH and selected portions of inner IP packet plus IP header and IPv6 selected portions of extension headers outer IP header Encrypts IP payload and Encrypts inner IPESP any IPv6 extesion header packet Encrypts IP payload and Encrypts inner IPESP with any IPv6 extesion packet. Authenticatesauthentication header. Authenticates IP inner IP packet. payload but no IP header Henric Johnson 14
  15. 15. Before applying AH Henric Johnson 15
  16. 16. Transport Mode (AH Authentication) Henric Johnson 16
  17. 17. Tunnel Mode (AH Authentication) Henric Johnson 17
  18. 18. Authentication Header• Provides support for data integrity and authentication (MAC code) of IP packets.• Guards against replay attacks. Henric Johnson 18
  19. 19. End-to-end versus End-to-Intermediate Authentication Henric Johnson 19
  20. 20. Encapsulating Security Payload • ESP provides confidentiality services Henric Johnson 20
  21. 21. 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 Henric Johnson 21
  22. 22. ESP Encryption and Authentication Henric Johnson 22
  23. 23. ESP Encryption and Authentication Henric Johnson 23
  24. 24. Combinations of Security Associations Henric Johnson 24
  25. 25. Combinations of Security Associations Henric Johnson 25
  26. 26. Combinations of Security Associations Henric Johnson 26
  27. 27. Combinations of Security Associations Henric Johnson 27
  28. 28. Key Management• Two types: – Manual – Automated • Oakley Key Determination Protocol • Internet Security Association and Key Management Protocol (ISAKMP) Henric Johnson 28
  29. 29. Oakley• Three authentication methods: – Digital signatures – Public-key encryption – Symmetric-key encryption Henric Johnson 29
  30. 30. ISAKMPHenric Johnson 30
  31. 31. 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 Henric Johnson 31

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