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IPsec: Internet Protocol Security
Chong, Luon, Prins, Trotter
What is IPsec?
• A collection of protocols for securing
Internet Protocol (IP) communications
by encrypting and authenticating all IP
packets1
• Progressive standard
• Defined in RFC 2401 thru 2409
• Purpose:
– To protect IP packets
– To provide defense against network attacks
1: From wikipedia.org
What is IPsec? (cont)
• Created November 1998
• Created by the Internet Engineering Task
Force (IETF)
• Deployable on all platforms
– Windows
– Unix
– Etc..
• Can be implemented and deployed on:
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End hosts
Gateways
Routers
Firewalls
Protection Against Attacks
• Layer 3 (network) protection
• Protects from:
– sniffers by encrypting data
– data modifications by using cryptography
based checksums
– identity spoofing, denial of service,
application layer, and password based
attacks through mutual authentication
– man in the middle attacks by mutual
authentication and cryptography based keys
How IPsec Works
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Services
Protocol Types
Key Protection
Components
Policy Based Security
Model Example
How IPsec Works: Services
• Security Properties
– Non-repudiation & Authentication
• Public key certificate based authentication
• Pre-shared key authentication
– Anti-replay
• Key management
• Diffie-Hellman Algorithm, Internet Key Exchange (IKE)
– Integrity
• Hash message authentication codes (HMAC)
– Confidentiality
• Public key cryptography
How IPsec Works: Protocol Types
• Authentication header (AH)
– Authentication, integrity, and anti-replay
– Placed between the IP layer and the
transport layer
Header Fields
Protection
How IPsec Works: Protocol Types (cont.)
• Encapsulating security payload (ESP)
– Provides confidentiality in addition to what
AH provides
– Has:
• Header
• Trailer
• Authentication Trailer
Header Fields
Protection
How IPsec Works: Components
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IPsec Policy Agent Service
Diffie-Hellman Algorithm
Internet Key Exchange (IKE)
Security Association (SA)
– Phase 1 SA
– Phase 2 SA
• IPsec Driver
How IPsec Works: Key Protection
• Key lifetimes
• Session key refresh limit
• Perfect forward security (PFS)
How IPsec Works: Policy Based Security
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Rules
Filter list
Filter actions
Policy Inheritance
Authentication
How IPsec Works: Model Example
Practical Implementations
• LANs, WANs, and remote connections
– VPNs for remote access
– Dial-up setting to private networks
– Where data security is critical
• Example: Hospital with patient data
• Businesses with multiple sites
Suggested Readings
• http://en.wikipedia.org/wiki/IPSEC
• http://www.ietf.org/rfc/rfc2401.txt
• http://www.webopedia.com/TERM/I/IPsec.html
• http://www.microsoft.com/windows2000/techinfo/p
lanning/security/ipsecsteps.asp
• Microsoft Windows 2000 Server TCP/IP Core
Networking Guide