32.1

Chapter 32

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Security in the Internet:�IPSec, SSL/TLS, PGP,�VPN, and Firewalls

32.2

Figure 32.1 Common structure of three security protocols

32.3

32-1 IPSecurity (IPSec)

IPSecurity (IPSec) is a collection of protocols designed by the Internet Engineering Task Force (IETF) to provide security for a packet at the network level.

Two Modes�Two Security Protocols�Security Association�Internet Key Exchange (IKE)

Virtual Private Network

Topics discussed in this section:

32.4

Figure 32.2 TCP/IP protocol suite and IPSec

32.5

Figure 32.3 Transport mode and tunnel modes of IPSec protocol

32.6

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

32.7

Figure 32.4 Transport mode in action

32.8

Figure 32.5 Tunnel mode in action

32.9

IPSec in tunnel mode protects the original IP header.

32.10

Figure 32.6 Authentication Header (AH) Protocol in transport mode

32.11

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

32.12

Figure 32.7 Encapsulating Security Payload (ESP) Protocol in transport mode

32.13

ESP provides source authentication, data integrity, and privacy.

32.14

Table 32.1 IPSec services

32.15

Figure 32.8 Simple inbound and outbound security associations

32.16

IKE creates SAs for IPSec.

32.17

Figure 32.9 IKE components

32.18

Table 32.2 Addresses for private networks

32.19

Figure 32.10 Private network

32.20

Figure 32.11 Hybrid network

32.21

Figure 32.12 Virtual private network

32.22

Figure 32.13 Addressing in a VPN

32.23

32-2 SSL/TLS

Two protocols are dominant today for providing security at the transport layer: the Secure Sockets Layer (SSL) Protocol and the Transport Layer Security (TLS) Protocol. The latter is actually an IETF version of the former.

SSL Services

Security Parameters�Sessions and Connections�Four Protocols

Transport Layer Security

Topics discussed in this section:

32.24

Figure 32.14 Location of SSL and TLS in the Internet model

32.25

Table 32.3 SSL cipher suite list

32.26

Table 32.3 SSL cipher suite list (continued)

32.27

The client and the server have six different cryptography secrets.

32.28

Figure 32.15 Creation of cryptographic secrets in SSL

32.29

Figure 32.16 Four SSL protocols

32.30

Figure 32.17 Handshake Protocol

32.31

Figure 32.18 Processing done by the Record Protocol

32.32

32-3 PGP

One of the protocols to provide security at the application layer is Pretty Good Privacy (PGP). PGP is designed to create authenticated and confidential �e-mails.

Security Parameters�Services�A Scenario�PGP Algorithms

Key Rings

PGP Certificates

Topics discussed in this section:

32.33

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

32.34

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

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

32.35

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

32.36

Table 32.4 PGP Algorithms

32.37

Figure 32.21 Rings

32.38

In PGP, there can be multiple paths from fully or partially trusted authorities to any subject.

32.39

32-4 FIREWALLS

All previous security measures cannot prevent Eve from sending a harmful message to a system. To control access to a system, we need firewalls. A firewall is a device installed between the internal network of an organization and the rest of the Internet. It is designed to forward some packets and filter (not forward) others.

Packet-Filter Firewall�Proxy Firewall

Topics discussed in this section:

32.40

Figure 32.22 Firewall

32.41

Figure 32.23 Packet-filter firewall

32.42

A packet-filter firewall filters at the network or transport layer.

32.43

Figure 32.24 Proxy firewall

32.44

A proxy firewall filters at the �application layer.