Cryptography and Network Security Overview & Chapter 1. Network Security. Chapter 0 Reader s s Guide. Standards Organizations.

(1)

Cryptography and

Network Security

Overview & Chapter 1

Fifth Edition

by William Stallings

Lecture slides by Lawrie Brown

(with edits by RHB)

Chapter 0 Chapter 0 –

–

Reader

’s Guide

’

s Guide

The art of war teaches us to rely not on the

likelihood of the enemy's not coming, but

on our own readiness to receive him; not

on the chance of his not attacking, but

rather on the fact that we have made our

position unassailable.

—

The Art of War,

Sun Tzu

Roadmap

•

• Cryptographic algorithms

Cryptographic algorithms

–

–symmetric cipherssymmetric ciphers –

–asymmetric encryptionasymmetric encryption –

–hash functionshash functions

•

• Mutual Trust

Mutual Trust

•

• Network Security

Network Security

•

• Computer Security

Computer Security

Standards Organizations

•

• National Institute of Standards &

National Institute of Standards &

Technology (NIST)

•

• Internet Society (ISOC)

Internet Society (ISOC)

•

• International Telecommunication Union

International Telecommunication Union

Telecommunication Standardization

Sector (ITU

Sector (ITU-

-T)

T)

•

• International Organization for

International Organization for

Standardization (ISO)

(2)

Chapter 1 Chapter 1 –

–

Introduction

•

• The combination of space, time, and

The combination of space, time, and

strength that must be considered as the

basic elements of this theory of defense

makes this a fairly complicated matter.

Consequently, it is not easy to find a fixed

point of departure.

point of departure..

.

—

On War, Carl Von Clausewitz

Outline

We will look at:

•

• topic roadmap & standards organizations

topic roadmap & standards organizations

•

• security concepts:

security concepts:

–

– confidentiality, integrity, availabilityconfidentiality, integrity, availability

•

• X.800 security architecture

X.800 security architecture

•

• security attacks, services, mechanisms

security attacks, services, mechanisms

•

• models for network (access) security

models for network (access) security

Computer Security

•

• the protection afforded to an automated

the protection afforded to an automated

information system in order to attain the

applicable objectives of preserving the

integrity, availability and confidentiality of

information system resources (includes

hardware, software, firmware,

information/data, and telecommunications)

(3)

Key Security Concepts

Levels of Impact

•

• can define 3 levels of impact from a

can define 3 levels of impact from a

security breach

– –LowLow – –ModerateModerate – –HighHigh

Examples of Security

Requirements

•

• confidentiality –

confidentiality

–

student grades

•

• integrity –

integrity

–

patient information

•

(4)

Computer Security Challenges

1.

1. not simplenot simple 2.

2. must consider potential attacksmust consider potential attacks 3.

3. procedures used counterprocedures used counter--intuitiveintuitive 4.

4. involve algorithms and secret infoinvolve algorithms and secret info 5.

5. must decide where to deploy mechanismsmust decide where to deploy mechanisms 6.

6. battle of wits between attacker / adminbattle of wits between attacker / admin 7.

7. not perceived not perceived ofof benefit until failsbenefit until fails 8.

8. requires regular monitoringrequires regular monitoring 9.

9. too often an aftertoo often an after--thoughtthought 10.

10. regarded as impediment to using systemregarded as impediment to using system

OSI Security Architecture

•

• ITU-

ITU

-T X.800

T X.800 “

“Security Architecture for OSI

Security Architecture for OSI”

”

•

• defines a systematic way of defining and

defines a systematic way of defining and

providing security requirements

•

• for us it provides a useful, if abstract,

for us it provides a useful, if abstract,

overview of concepts we will study

Aspects of Security

•

• consider 3 aspects of information security:

consider 3 aspects of information security:

–

–security attacksecurity attack

–

–security mechanismsecurity mechanism

–

–security servicesecurity service

•

• note terms

note terms

–

–threat threat ––a potential for violation of securitya potential for violation of security –

–attack attack ––an assault on system security, a an assault on system security, a deliberate attempt to evade security services deliberate attempt to evade security services

Passive Attacks

(5)

Active Attacks

(6)

Security Service

–

–enhance security of data processing systems enhance security of data processing systems and information transfers of an organization and information transfers of an organization –

–intended to counter security attacksintended to counter security attacks –

–using one or more security mechanisms using one or more security mechanisms –

–often replicates functions normally associated often replicates functions normally associated with physical documents

with physical documents

•

• which, for example, have signatures, dates; need which, for example, have signatures, dates; need protection from disclosure, tampering, or

protection from disclosure, tampering, or destruction; be notarized or witnessed; be destruction; be notarized or witnessed; be recorded or licensed recorded or licensed

Security Services

•

• X.800:

X.800:

“

“a service provided by a protocol layer of a service provided by a protocol layer of

communicating open systems, which ensures communicating open systems, which ensures adequate security of the systems or of data adequate security of the systems or of data transfers

transfers””

•

• RFC 2828:

RFC 2828:

“

“a processing or communication service a processing or communication service

provided by a system to give a specific kind of provided by a system to give a specific kind of protection to system resources

protection to system resources””

Security Services (X.800)

•

• AuthenticationAuthentication--assurance that communicating assurance that communicating entity is the one claimed

entity is the one claimed

–

– have both peer-have both peer-entity & data origin authenticationentity & data origin authentication

•

• Access ControlAccess Control--prevention of the prevention of the unauthorized use of a resource unauthorized use of a resource •

• Data ConfidentialityData Confidentiality--protection of data from protection of data from unauthorized disclosure

unauthorized disclosure •

• Data IntegrityData Integrity--assurance that data received is assurance that data received is as sent by an authorized entity

as sent by an authorized entity •

• NonNon--RepudiationRepudiation --protection against denial by protection against denial by one of the parties in a communication

one of the parties in a communication •

• AvailabilityAvailability--resource accessible/usableresource accessible/usable

Security Mechanism

•

• feature designed to detect, prevent, or

feature designed to detect, prevent, or

recover from a security attack

•

• no single mechanism that will support all

no single mechanism that will support all

services required

•

• however one particular element underlies

however

one particular element underlies

many of the security mechanisms in use:

–

– cryptographic techniquescryptographic techniques

•

(7)

Security Mechanisms (X.800)

•

• specific security mechanisms:

specific security mechanisms:

–

–encipherment, digital signatures, access encipherment, digital signatures, access controls, data integrity, authentication controls, data integrity, authentication exchange, traffic padding, routing control, exchange, traffic padding, routing control, notarization

notarization

•

• pervasive security mechanisms:

pervasive security mechanisms:

–

–trusted functionality, security labels, event trusted functionality, security labels, event detection, security audit trails, security detection, security audit trails, security recovery

recovery

Model for Network Security

•

• using this model requires us to:

using this model requires us to:

1.

1. design a suitable algorithm for the security design a suitable algorithm for the security transformation

transformation 2.

2. generate the secret information (keys) used generate the secret information (keys) used by the algorithm

by the algorithm 3.

3. develop methods to distribute and share the develop methods to distribute and share the secret information

secret information 4.

4. specify a protocol enabling the principals to specify a protocol enabling the principals to use the transformation and secret

use the transformation and secret information for a security service information for a security service

Model for Network Access Security

(8)

Model for Network Access Security

•

• using this model requires us to:

using this model requires us to:

1.

1. select appropriate gatekeeper functions to select appropriate gatekeeper functions to identify users

identify users 2.

2. implement security controls to ensure only implement security controls to ensure only authorised users access designated

authorised users access designated information or resources