IPSec

• IPSec


  Offers authentication, confidentiality, integrity, access control, and protection against replay attacks
• IPSec


  • Operates on network layer, transparent to the user
  • Automatically negotiates cryptographic protection with another IPSec enabled computer
• IPSec negotiation


  1. Both ends negotiate cryptographic parameters and assurance, complete authentication, and agree on shared secret keys

  2. Provide data encryption confidentiality and message integrity
• Security Association (SA)


  Contains secret keys, names of cryptographic algorithms for encryption and authentication, and other parameters
• IPSec Phase 1


  1. Authentication

  2. Key Agreement

  3. SA-1 parameters are derived
• IPSec Phase 2

  1. Negotiation of bulk data encryption parameters

  2. SA-2 parameters are derived
• SA-1 parameters


  Used to encrypt and authenticate Phase 2 messages
• SA-2 parameters


  Used to encrypt and authenticate all Phase 2 messages
• Transport Mode


  IPSec protects what is delivered from the transport layer to the network layer, but does not protect the IP Header
• Tunnel Mode


  IPSec protects the entire IP packet, including the header, by applying IPSec security methods and adding a new IP Header
• Authentication Header (AH) Protocol


  Provides data integrity and source authentication, but not confidentiality
• Encapsulating Security Payload (ESP) Protocol


  Provides confidentiality, data integrity, and source authentication
• IPSec combinations

  • ESP + Transport
  • ESP + Tunnel
  • AH + Transport
  • AH + Tunnel
• The most robust protection is ESP + Tunnel, often used for VPNs
• Services provided by IPSec

  • Access Control
  • Message Authentication
  • Entity Authentication
  • Confidentiality
  • Replay attack protection
• Two-phase key exchange in IPSec

  • Single SA-1 can generate many SA-2
  • Fast changes in SA-2 keys
  • Encryption algorithms in SA-2 can be changed