1 IPSec IPSec provides the capability to secure communications across a LAN, across private and public wide area networks (WANs) and across the Internet.

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IPSec

IPSec provides the capability to secure communications across a LAN, across private and public wide area networks

(WANs) and across the Internet

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Usability and Security

Security

Convenience / Usability

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Determine where on this

line your organization

needs lie

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Services, Mechanisms, Algorithms

A typical security protocol provides one or more security services (authentication, secrecy, integrity, etc.)

Services are built from mechanisms. Mechanisms are implemented using algorithms.

SSL/IPSec/PPTP, etc

Signatures Encryption Hashing

DSA RSA RSA DES SHA1 MD5

Services (Security Protocols)

Mechanisms

Algorithms

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Security in the Internet Architecture

Lack of security in the Internet Architecture Security was left up to the applications With the passage of time it was realized that

universal security at the IP level will become a need and not a luxury

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Security Protocol Layers

Application

Presentation

Session

Transport

Netw ork

Datalink

Physical

Application

Presentation

Session

Transport

Netw ork

Datalink

Physical

Email - S/M IM E

SSL

IPSec

PPP - ECP

PHYSICAL NETW ORKEncrypting

NICEncrypting

NIC

•The further down you go, the more transparent it is

•The further up you go, the easier it is to deploy

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Some Pros of Security at the IP Level

Can be end to end or at least multi link unlike link layer

Could be hw/sw supported (hw support for encryption)

Can shield unmodified host apps giving them crypto/security at the level of nets/hosts/and possibly users

Can extend secure enclave across insecure areas

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What is IPSec? Extensions to the basis Internet Protocol to

provide security functions at the IP level Applicable to both IP Version 4 and IP Version

6 IPSec available in Windows 2000, Linux, Cisco

Routers, etc.

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How do you know IPSec is there?

AH/ESP new IP layer protocols (50/51) with either 1. an IP datagram encapsulated in them (tunnel mode) 2. TCP/UDP and the rest above them (transport mode)

Every packet may have AH/ESP applied to them:AH for authentication; ESP for encryption and authentication, this is bulk/per

packet encryption/authentication

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IP Security Usage Scenario

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Applications of IPSec Secure Branch Office Connectivity Over the

Internet Secure Remote Access Over the Internet Establishing Extranet and Intranet Connectivity

with Business partners Enhancing Electronic Commerce Security

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IP Security Architecture Defined by IPSec Documents (RFCs) IP Security Protocol Working Group of IETF IP Security Evolving with the passage of time IPSec provides security services at the IP layer

by enabling a system to select required security protocols, determine the algorithms to use for the services, and put in place any cryptographic keys required.

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IPSec Documents Overview Relevant RFCs RFC 1825: An overview of a

security architecture RFC 1826: Description of a

packet authentication extension to IP

RFC 1828: A specific authentication mechanism

RFC 1827: Description of a packet encryption extension to IP

RFC 1829: A specific encryption mechanism

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AH and ESP AH

The Authentication Header provides support for data integrity and authentication of IP packets

ESPThe Encapsulating Security Payload provides

confidentiality services, including confidentiality of message contents and limited traffic flow confidentiality. As an optional feature, ESP can also provide the same authentication service as AH.

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IPSec Services

IPSec Framework Protocols

All data is in plaintext.R1 R2

Data payload is encrypted.R1 R2

Authentication Header

Encapsulating Security Payload

AH provides the following: Authentication

Integrity

ESP provides the following: Encryption

Authentication

Integrity

IPSec Framework

Diffie-Hellman DH7

DH7Diffie-Hellman

Confidentiality

Key length: - 56-bits

Key length: - 56-bits (3 times)

Key length: - 160-bits

Key lengths: -128-bits-192 bits-256-bits

Least secure Most secure

DH7Diffie-Hellman

Integrity

Key length: - 128-bits

Key length: - 160-bits)

Least secure Most secure

DH7Diffie-Hellman

Authentication

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Security Associations What is a SA?

An SA is a one way relationship between a sender and a received that affords security services to the traffic carried on it.

SA ParametersSecurity Association Database stores parameters

associated with each of the SAs SA Selectors

Each SPD entry is defined by a set of IP and upper layer protocol field values called selectors.

Security Association (SA) A simplex (uni-directional) logical connection, created

for security purposes All traffic traversing an SA is provided the same

security processing In IPsec, an SA is an Internet-layer abstraction

implemented through the use of AH or ESP State data associated with an SA is represented in the

SA Database (SAD)

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Security Parameters Index (SPI) An arbitrary 32-bit value that is used by a receiver to identify the SA to

which an incoming packet should be bound. For a unicast SA, the SPI can be used by itself to specify an SA, or it may be

used in conjunction with the IPsec protocol type. Additional IP address information is used to identify multicast SAs. The SPI is carried in AH and ESP protocols to enable the receiving system

to select the SA under which a received packet will be processed. An SPI has only local significance, as defined by the creator of the SA (usually the receiver of the packet carrying the SPI); thus an SPI is generally

viewed as an opaque bit string. However, the creator of an SA may choose to interpret the bits in an SPI to

facilitate local processing.

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Security Association Database Parameters

Security Parameters Index (SPI) • sequence number counter • sequence number overflow • anti-replay window • AH information • ESP information • lifetime of SA • IPSec protocol mode • Path MTU • other information

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SA Selector IPSec provides flexibility • SAs can be combined • Security Policy Database (SPD) specifies mapping of IP traffic to SAs • mapping is done according to field values of selectors – destination IP address – source IP address – user ID – data sensitivity level – transport layer protocol – source and destination ports

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Transport and Tunnel Modes

Tunnel Mode means that one outgoing IP packet is encapsulated in another packet with typically a different IP destination

Tunnels can be (1) Router to Router (2) Router to host or host to router (3) host to host

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Transport and Tunnel Modes

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Tunnel Mode and Transport Mode Functionality

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Authentication Header

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Services Provided by AH Anti-Replay Service Integrity Check Value

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Anti-Replay Service

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Transport and Tunnel Modes

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Scope of Authentication Header

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Scope of Authentication Header

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Encapsulating Security Payload - ESP

ESP ServicesConfidentialityAuthentication Services

ESP FormatSPISNPDPaddingPad LengthNext HeaderAuthentication Data

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ESP

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ESP Format

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Transport-level security

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A virtual private network via Tunnel Mode