IP SEC

Edited by Akhyari Nasir

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.

• 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 http://sce.uhcl.edu/yang/teaching/.

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IP Security Scenario

http://sce.uhcl.edu/yang/teaching/.

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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 http://sce.uhcl.edu/yang/teaching/.

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Goal/Services of IPsec

• Provides

security services

at IP layer – Access Control – Connectionless integrity – Data origin authentication – Rejection of replayed packets – Confidentiality (encryption) – Limited traffic flow confidentiallity

IPsec Architecture

• Components – Security Protocols – Security Associations – Key Management – Algorithms for authentication and encryption

Security Protocols

• Authentication Header (AH) – Data Origin Authentication – Anti-replay service – Data Integrity • Encapsulating Security Payload (ESP) – Confidentiality – Data Origin Authentication – Anti-replay service – Connectionless Integrity

AH

• AH provides authentication for as much of the IP header as possible, as well as for upper level protocol data • Tow modes: transport mode/tunnel mode

IP Security (IPSec)

• Different security tools function at different layers of the Open System Interconnection (OSI) model • Secure/Multipurpose Internet Mail Extensions (S/MIME) and Pretty Good Privacy (PGP) operate at the Application layer • Kerberos functions at the Session layer

IP Security (IPSec) (continued)

IP Security (IPSec) (continued)

• IPSec is a set of protocols developed to support the secure exchange of packets • Considered to be a transparent security protocol • Transparent to applications, users, and software • Provides three areas of protection that correspond to three IPSec protocols: – Authentication – Confidentiality – Key management

IP Security (IPSec) (continued)

• Supports two encryption modes: – Transport mode encrypts only the data portion (payload) of each packet, yet leaves the header encrypted – Tunnel mode encrypts both the header and the data portion • IPSec accomplishes transport and tunnel modes by adding new headers to the IP packet • The entire original packet is then treated as the data portion of the new packet

IP Security (IPSec) (continued)

IP Security (IPSec) (continued)

• Both Authentication Header (AH) and Encapsulating Security Payload (ESP) can be used with Transport or Tunnel mode, creating four possible transport mechanisms: – AH in transport mode – AH in tunnel mode – ESP in transport mode – ESP in tunnel mode

Figure 32.2

TCP/IP protocol suite and IPSec

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Figure 32.3

Transport mode and tunnel modes of IPSec protocol

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Note

IPSec in the transport mode does not protect the IP header; it only protects the information coming from the transport layer.

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Figure 32.4

Transport mode in action

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Figure 32.5

Tunnel mode in action

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Note

IPSec in tunnel mode protects the original IP header.

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Figure 32.6

Authentication Header (AH) Protocol in transport mode

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Note

The AH Protocol provides source authentication and data integrity, but not privacy.

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Figure 32.7

Encapsulating Security Payload (ESP) Protocol in transport mode

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Note

ESP provides source authentication, data integrity, and privacy.

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Table 32.1

IPSec services

Figure 32.8

Simple inbound and outbound security associations

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Note

IKE creates SAs for IPSec.

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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 http://sce.uhcl.edu/yang/teaching/.

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AH ESP Transport Mode SA Tunnel Mode SA Authenticates IP payload and selected portions of IP header and IPv6 extension headers Encrypts IP payload and any IPv6 extesion header Authenticates entire inner IP packet plus selected portions of outer IP header Encrypts inner IP packet ESP with authentication Encrypts IP payload and any IPv6 extesion header. Authenticates IP payload but no IP header Encrypts inner IP packet. Authenticates inner IP packet.

http://sce.uhcl.edu/yang/teaching/.

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Key Management

• Two types: – Manual – Automated •

Oakley

Key Determination Protocol • Internet Security Association and Key Management Protocol (

ISAKMP

) http://sce.uhcl.edu/yang/teaching/.

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Oakley

• Three authentication methods: – Digital signatures – Public-key encryption – Symmetric-key encryption (aka. Preshare key) http://sce.uhcl.edu/yang/teaching/.

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ISAKMP

http://sce.uhcl.edu/yang/teaching/.

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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 http://sce.uhcl.edu/yang/teaching/.

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