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IP SecurityIP Security

Outline of the session

– IP Security Overview– IP Security Architecture– Key Management

Based on slides by Dr. Lawrie Brown of the Australian Defence Force Academy, University College, UNSW

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What Does IPSec Do??What Does IPSec Do??

• Provides security services at the IP layer for other TCP/IP protocols and applications to use.

• Provides the tools that devices on a TCP/IP need in order to communicate securely.

• It allows 2 devices to set up a secure path that may traverse across many insecure intermediate systems.

• Performs (at least) the following tasks:

– Defines the set of security protocols to use, so that each one sends data in a format the other can understand.

– Defines the specific encryption algorithm to use in encoding data.

– Enables key exchange to “unlock” the encrypted data

• Once this background work is completed, each device must use the protocols, methods and keys previously agreed upon to encode data and send it across the network

Based on slides by Dr. Lawrie Brown of the Australian Defence Force Academy, University College, UNSW

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How Does It Do This?How Does It Do This?

• IPSec Authentication Header (AH):– Provides authentication services for IPSec.– All of

• Originator verification• Data integrity• Protection against replay attacks

• Encapsulating Security Payload (ESP): – Encrypts the payload of the IP datagram. – Can be used with or without authentication

Based on slides by Dr. Lawrie Brown of the Australian Defence Force Academy, University College, UNSW

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Functions Supported by..Functions Supported by..

• Encryption/Hashing Algorithms: – AH and ESP

• Generic, do not specify the exact mechanism used for encryption.

• Negotiate which algorithms are used.. • Commonly use MD5 and SHA-1.

• Security Policies and Associations, and Management Methods: – Security Associations (SA) record algorithms and other

parameters for a one-way exchange between 2 principals– Security Policies define the way the SAs are applied at

the packet level– SAs can be bundled to exchange SA information

• Key Exchange Framework and Mechanism:– Uses Internet Key Exchange (IKE)

Based on slides by Dr. Lawrie Brown of the Australian Defence Force Academy, University College, UNSW

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Implementation choicesImplementation choices

• End-to-end? Network Infrastructure?

– Fully integrate with IP?– Implement in software?– Implement in hardware?

• And apply it in tunnel or transport mode– (See later)

Based on slides by Dr. Lawrie Brown of the Australian Defence Force Academy, University College, UNSW

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IP Security OverviewIP 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

Based on slides by Dr. Lawrie Brown of the Australian Defence Force Academy, University College, UNSW

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IP Security ScenarioIP Security Scenario

Based on slides by Dr. Lawrie Brown of the Australian Defence Force Academy, University College, UNSW

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IP Security OverviewIP 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

Based on slides by Dr. Lawrie Brown of the Australian Defence Force Academy, University College, UNSW

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IP Security ArchitectureIP Security Architecture

• IPSec documents:– RFC 2401: An overview of security

architecture– RFC 2402: Description of a packet

authentication extension to IPv4 and IPv6

– RFC 2406: Description of a packet encryption extension to IPv4 and IPv6

– RFC 2408: Specification of key management capabilities

Based on slides by Dr. Lawrie Brown of the Australian Defence Force Academy, University College, UNSW

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IPSec Document OverviewIPSec Document Overview

DOI = Domain of Interpretation

Based on slides by Dr. Lawrie Brown of the Australian Defence Force Academy, University College, UNSW

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IPSec ServicesIPSec Services

• Access Control• Connectionless integrity• Data origin authentication• Rejection of replayed packets• Confidentiality (encryption)• Limited traffic flow confidentiallity

Based on slides by Dr. Lawrie Brown of the Australian Defence Force Academy, University College, UNSW

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Security Associations (SA)Security Associations (SA)

• A one way relationship between a sender and a receiver.

• Identified by three parameters:– Security Parameter Index (SPI)– IP Destination address– Security Protocol Identifier

Based on slides by Dr. Lawrie Brown of the Australian Defence Force Academy, University College, UNSW

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Authentication HeaderAuthentication Header

• Provides support for data integrity and authentication (MAC code) of IP packets.

• Guards against replay attacks.

Based on slides by Dr. Lawrie Brown of the Australian Defence Force Academy, University College, UNSW

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Transport Mode (AH Authentication)Transport Mode (AH Authentication)

Before AH

After AH

Based on slides by Dr. Lawrie Brown of the Australian Defence Force Academy, University College, UNSW

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Tunnel Mode (AH Authentication)Tunnel Mode (AH Authentication)

Before AH

After AH

Based on slides by Dr. Lawrie Brown of the Australian Defence Force Academy, University College, UNSW

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End-to-end versus End-to-Intermediate End-to-end versus End-to-Intermediate AuthenticationAuthentication

Based on slides by Dr. Lawrie Brown of the Australian Defence Force Academy, University College, UNSW

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Encapsulating Security PayloadEncapsulating Security Payload

• ESP provides confidentiality services

Based on slides by Dr. Lawrie Brown of the Australian Defence Force Academy, University College, UNSW

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Encryption and Authentication Encryption and Authentication AlgorithmsAlgorithms

• Encryption:– Three-key triple DES– RC5– IDEA– Three-key triple IDEA– CAST– Blowfish

• Authentication:– HMAC-MD5-96– HMAC-SHA-1-96

Based on slides by Dr. Lawrie Brown of the Australian Defence Force Academy, University College, UNSW

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ESP Encryption and AuthenticationESP Encryption and Authentication

Based on slides by Dr. Lawrie Brown of the Australian Defence Force Academy, University College, UNSW

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ESP Encryption and AuthenticationESP Encryption and Authentication

Based on slides by Dr. Lawrie Brown of the Australian Defence Force Academy, University College, UNSW

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Key ManagementKey Management

• Two types:– Manual– Automated

• Oakley Key Determination Protocol• Internet Security Association and Key

Management Protocol (ISAKMP)

Based on slides by Dr. Lawrie Brown of the Australian Defence Force Academy, University College, UNSW

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OakleyOakley

• Three authentication methods:– Digital signatures– Public-key encryption– Symmetric-key encryption

Based on slides by Dr. Lawrie Brown of the Australian Defence Force Academy, University College, UNSW

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ISAKMPISAKMP

Based on slides by Dr. Lawrie Brown of the Australian Defence Force Academy, University College, UNSW

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TCP/IP ExampleTCP/IP Example

Based on slides by Dr. Lawrie Brown of the Australian Defence Force Academy, University College, UNSW