Chapter 32

Security in the Internet:IPSec, SSL/TLS, PGP,

VPN and FirewallsVPN, and Firewalls

32.1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Figure 32.1 Common structure of three security protocols

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3232--1 1 IPSecurity (IPSec)IPSecurity (IPSec)y ( )y ( )

IPSecurityIPSecurity (IPSec)(IPSec) isis aa collectioncollection ofof protocolsprotocols designeddesignedbyby thethe InternetInternet EngineeringEngineering TaskTask ForceForce (IETF)(IETF) totoprovideprovide securitysecurity forfor aa packetpacket atat thethe networknetwork levellevel..

Topics discussed in this section:Topics discussed in this section:Two ModesTwo Security ProtocolsSecurity AssociationInternet Key Exchange (IKE)Virtual Private Network

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Virtual Private Network

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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N t

IPSec in the transport mode does not

Note

IPSec in the transport mode does not protect the IP header; it only protects

h i f i i f hthe information coming from the transport layer.p y

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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 i i l IP h doriginal 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 th ti ti d d t i t itauthentication 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, d t i t it d idata integrity, and privacy.

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Table 32.1 IPSec services

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Figure 32.8 Simple inbound and outbound security associations

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N t

IKE creates SAs for IPSec

Note

IKE creates SAs for IPSec.

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Figure 32.9 IKE components

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Table 32.2 Addresses for private networks

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Figure 32.10 Private network

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Figure 32.11 Hybrid network

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Figure 32.12 Virtual private network

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Figure 32.13 Addressing in a VPN

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3232--2 2 SSL/TLSSSL/TLS

TwoTwo protocolsprotocols areare dominantdominant todaytoday forfor providingprovidingTwoTwo protocolsprotocols areare dominantdominant todaytoday forfor providingprovidingsecuritysecurity atat thethe transporttransport layerlayer:: thethe SecureSecure SocketsSocketsLayerLayer (SSL)(SSL) ProtocolProtocol andand thethe TransportTransport LayerLayerLayerLayer (SSL)(SSL) ProtocolProtocol andand thethe TransportTransport LayerLayerSecuritySecurity (TLS)(TLS) ProtocolProtocol.. TheThe latterlatter isis actuallyactually ananIETFIETF versionversion ofof thethe formerformerIETFIETF versionversion ofof thethe formerformer..

Topics discussed in this section:Topics discussed in this section:SSL ServicesSecurity ParametersSessions and ConnectionsFour ProtocolsTransport Layer Security

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Transport Layer Security

Figure 32.14 Location of SSL and TLS in the Internet model

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Table 32.3 SSL cipher suite listTable 32.3 SSL cipher suite list

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T bl 32 3 SS i h i li ( i d)Table 32.3 SSL cipher suite list (continued)

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Note

The client and the server have six diff t t h tdifferent cryptography secrets.

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Figure 32.15 Creation of cryptographic secrets in SSL

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Figure 32.16 Four SSL protocols

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Figure 32.17 Handshake Protocol

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Figure 32.18 Processing done by the Record Protocol

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3232--3 3 PGPPGP

OneOne ofof thethe protocolsprotocols toto provideprovide securitysecurity atat thetheOneOne ofof thethe protocolsprotocols toto provideprovide securitysecurity atat thetheapplicationapplication layerlayer isis PrettyPretty GoodGood PrivacyPrivacy (PGP)(PGP).. PGPPGP isisdesigneddesigned toto createcreate authenticatedauthenticated andand confidentialconfidentialdesigneddesigned toto createcreate authenticatedauthenticated andand confidentialconfidentialee--mailsmails..

Security ParametersTopics discussed in this section:Topics discussed in this section:Security ParametersServicesA ScenarioPGP AlgorithmsKey RingsPGP C tifi t

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PGP Certificates

Figure 32.19 Position of PGP in the TCP/IP protocol suite

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Note

In PGP, the sender of the message needs to include the identifiers of theneeds to include the identifiers of the

algorithms used in the message as well as the values of the keysas the values of the keys.

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Figure 32.20 A scenario in which an e-mail message is authenticated and encryptedauthenticated and encrypted

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Table 32.4 PGP Algorithms

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Figure 32.21 Rings

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Note

In PGP, there can be multiple paths from G , t e e ca be u t p e pat s ofully or partially trusted authorities to

any subjectany subject.

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3232--4 4 FIREWALLSFIREWALLS

AllAll previousprevious securitysecurity measuresmeasures cannotcannot preventprevent EveEveAllAll previousprevious securitysecurity measuresmeasures cannotcannot preventprevent EveEvefromfrom sendingsending aa harmfulharmful messagemessage toto aa systemsystem.. ToTocontrolcontrol accessaccess toto aa systemsystem wewe needneed firewallsfirewalls AA firewallfirewallcontrolcontrol accessaccess toto aa system,system, wewe needneed firewallsfirewalls.. AA firewallfirewallisis aa devicedevice installedinstalled betweenbetween thethe internalinternal networknetwork ofof ananorganizationorganization andand thethe restrest ofof thethe InternetInternet ItIt isis designeddesignedorganizationorganization andand thethe restrest ofof thethe InternetInternet.. ItIt isis designeddesignedtoto forwardforward somesome packetspackets andand filterfilter (not(not forward)forward)othersothersothersothers..

Topics discussed in this section:Topics discussed in this section:Packet-Filter FirewallProxy Firewall

pp

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Figure 32.22 Firewall

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Figure 32.23 Packet-filter firewall

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Note

A packet-filter firewall filters at the t k t t lnetwork or transport layer.

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Figure 32.24 Proxy firewall

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Note

A proxy firewall filters at the li ti lapplication layer.

32.44