This document provides an overview of network and internet security, focusing on IP Security (IPsec) protocols. It discusses IPsec frameworks that ensure secure communications over the internet by providing authentication, confidentiality, and key management. The document describes IPsec protocols like Authentication Header (AH) and Encapsulating Security Payload (ESP) that provide data integrity and confidentiality. It also explains how IPsec establishes security associations and works in two phases using the Internet Key Exchange protocol to securely exchange keys and negotiate security parameters for authentication and encryption of network traffic.

1. Nadar Saraswathi college of
Arts and science Theni
Presented by:
S.Swetha
I M.sc(IT)
The Security Layer
Department of CS and iT

2. Network and internet
security

3. Index
•
Wireless Transport Layer Security (WTLS)
•
IP Security
•
IPsec Protocols
•
Internet Key Exchange (IKE) Protocol
•
Security Association (SA)
•
Authentication Header (AH)
•
Encapsulating Security Payload (ESP)
•
IPsec key management

4. Wireless Transport Layer
Security (WTLS)
•
It can be integrated into WAP(Wireless
Application Protocol) architecture on top of
WDP(Wireless Datagram Protocol).
•
It supports Datagram and connection
oriented transport layer protocols.
•
Based on TLS/SSL protocol.It can provide
different levels of security.
•
Privacy

6. IP Security

7. What is IP Security
•
Framework of open standards to ensure
secure communications over the Internet
In short: It is the network layer Internet
Security Protocol

8. IPSEC Service
Internet/
Intranet
IPSec disabled host
Case 1 : Insecure IP Packet
IPSec enabled host
Case 2 : Secure IP Packet
IP
Header
Upper
layer
data
IP
Header
IPSec
Header
Upper
layer
data

9. IPSec
•
general IP Security mechanisms
•
provides
–
authentication
–
confidentiality
–
key management
•
applicable to use over LANs, across public
& private WANs, & for the Internet

10. IP sec Application
•
IPSec provides the capability to secure
communications across a LAN, across private
and public WANs, and across the Internet.
–
Secure branch office connectivity over the Internet
–
Secure remote access over the Internet
–
Establishing extranet and intranet connectivity with partners
–
Enhancing electronic commerce security

11. Security Associations
•
One of the most important concepts in IPSec is called a
Security Association (SA). Defined in RFC 1825.
•
SAs are the combination of a given Security Parameter
Index (SPI) and Destination Address.
•
SAs are one way. A minimum of two SAs are required
for a single IPSec connection.
•
SAs contain parameters including:
–
Authentication algorithm and algorithm mode
–
Encryption algorithm and algorithm mode
–
Key(s) used with the authentication/encryption algorithm(s)
–
Lifetime of the key
–
Lifetime of the SA
–
Source Address(es) of the SA
–
Sensitivity level (ie Secret or Unclassified)

12. IP security scenario

13. scenario of IPSec usage
•
An organization maintains LANs at dispersed
locations
•
Non secure IP traffic is conducted on each LAN.
•
IPSec protocols are used
•
These protocols operate in networking devices
that connect each LAN to the outside world.
(router, firewall )
•
The IPSec networking device will typically
encrypt and compress all traffic going into the
WAN, and decrypt and decompress traffic
coming from the WAN

14. Why not use IPSec?
•
Processor overhead to encrypt & verify
each packet can be great.
•
Added complexity in network design.

15. Benefits of IPSec
•
in a firewall/router provides strong security
to all traffic crossing the perimeter
•
in a firewall/router is resistant to bypass
•
is below transport layer, hence transparent
to applications
•
can be transparent to end users
•
can provide security for individual users
•
secures routing architecture

16. IPsec

17. Network Layer Security
•
IP security (IPsec)
–
Two protocols
•
Authentication protocol, using an Authentication Header (AH)
•
Encryption/authentication protocol, called the Encapsulating
Security Payload (ESP)
–
Two modes of operation
•
Transport mode: provides protection for upper-layer
protocols
•
Tunnel mode: protects the entire IP datagram

18. IPSec protocols – AH protocol
•
AH - Authentication Header
–
Defined in RFC 1826
–
Integrity: Yes, including IP header
–
Authentication: Yes
–
Non-repudiation: Depends on cryptography algorithm.
–
Encryption: No
–
Replay Protection: Yes
IP Header AH Header Payload (TCP, UDP, etc)
IP Header AH Header Payload (TCP. UDP,etc)
IP Header
Transport Packet layout
Tunnel Packet layout

19. IPSec protocols – ESP protocol
•
ESP – Encapsulating Security Payload
–
Defined in RFC 1827
–
Integrity: Yes
–
Authentication: Depends on cryptography algorithm.
–
Non-repudiation: No
–
Encryption: Yes
–
Replay Protection: Yes
IP Header ESP Header Payload (TCP, UDP, etc)
IP Header ESP Header Payload (TCP. UDP,etc)
IP Header
Transport Packet layout
Tunnel Packet layout
Unencrypted Encrypted

20. What protocol to use?
•
Differences between AH and ESP:
–
ESP provides encryption, AH does not.
–
AH provides integrity of the IP header, ESP does not.
–
AH can provide non-repudiation. ESP does not.
•
However, we don’t have to choose since both
protocols can be used in together.
•
Why have two protocols?
–
Some countries have strict laws on encryption. If you
can’t use encryption in those countries, AH still
provides good security mechanisms. Two protocols
ensures wide acceptance of IPSec on the Internet.

21. Data Integrity and Confidentiality
Basic difference between AH and ESP

22. IPSec Protocols (cont)
Algorithms Used:
Encryption:
Symmetric – As IP packets may arrive out of order and
Asymmetric algorithms are incredible slow.
E.g. DES (Data Encryption Standard)

Authentication:
MAC (Message Authentication Codes) based on symmetric
encryption algorithms.
One way hash functions. (MD5 or SHA-1)

23. Transport Versus Tunnel Mode
Transport Mode:
•
Used for Peer to Peer communication security
•
Data is encrypted
Tunnel Mode:
•
Used for site-to-site communication security
•
Entire packet is encrypted.

24. Transport versus Tunnel mode
(cont)
Transport mode is used when the cryptographic endpoints are also the
communication endpoints of the secured IP packets.
Cryptographic endpoints: The entities that generate / process an IPSec header
(AH or ESP)
Communication endpoints: Source and Destination of an IP packet

25. Transport versus Tunnel mode
(cont)
Tunnel mode is used when at least one cryptographic endpoint is not a
communication endpoint of the secured IP packets.
Outer IP Header – Destination for the router.
Inner IP Header – Ultimate Destination

26. Transport Mode
Tunneling Mode

27. How IPSec works: Phase 1
•
Internet Key Exchange (IKE) is used to setup
IPSec.
•
IKE Phase 1:
–
Establishes a secure, authenticated channel between the two
computers
–
Authenticates and protects the identities of the peers
–
Negotiates what SA policy to use
–
Performs an authenticated shared secret keys exchange
–
Sets up a secure tunnel for phase 2
–
Two modes: Main mode or Aggressive mode
•
Main Mode IKE
.1
Negotiate algorithms & hashes.
.2
Generate shared secret keys using a Diffie-Hillman exchange.
.3
Verification of Identities.
•
Aggressive Mode IKE
–
Squeezes all negotiation, key exchange, etc. into less packets.
–
Advantage: Less network traffic & faster than main mode.

28. How IPSec works: Phase 2
–
An AH or ESP packet is then sent using the agreed
upon “main” SA during the IKE phase 1.
–
IKE Phase 2
•
Negotiates IPSec SA parameters
•
Establishes IPSec security associations for specific
connections (like FTP, telnet, etc)
•
Renegotiates IPSec SAs periodically
•
Optionally performs an additional Diffie-Hellman exchange

29. How IPSec works: Communication
•
Once Phase 2 has established an SA for a
particular connection, all traffic on that
connection is communicated using the SA.
•
IKE Phase 1 exchange uses UDP Port 500.
•
AH uses IP protocol 51.
•
ESP uses IP protocol 50.

30. Key Management