Chapter 1 introduction
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Chapter 1 - Introduction. Security Violations OSI Security Architecture Network Security Model. Security Violations. 1. Capture. File F is SENSITIVE F A -------> B C CAPTURES F. Security Violations. 2. Intercept - Update.

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Chapter 1 - Introduction

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Chapter 1 introduction

Chapter 1 - Introduction

  • Security Violations

  • OSI Security Architecture

  • Network Security Model


Security violations

Security Violations

1. Capture

File F is SENSITIVE

F

A -------> B

C CAPTURES F


Security violations1

Security Violations

2. Intercept - Update

Authorisation File F is SENSITIVE

A sends message to B: ”Update F with names”

A(m) m B(F)

C INTERCEPTS m and adds name of C

A(m) m C(m) m B(F)


Security violations2

Security Violations

3. Substitute

Authorisation File F is SENSITIVE

C PRETENDS to be A

C sends message to B: ”Update F with name of C”

{C}A(m) m B(F)


Security violations3

4. Intercept - Preempt

Security Violations

A sends message to B: ”STOP C’s r/w access”

A(m0) m0 B(m1)

B(m1) m1STOP(C)

C INTERCEPTS m0:

A(m0) m0 C m0 B(m1)

C(r/w ACCESS)

B(m1) m1STOP(C)


Security violations4

5. Denial

Security Violations

C sends message to B

C(m) m B

Later,

B QUERIES C about message

B m,? C

C DENIES sending message

C(m,?) NO B


Osi security architecture x 800 security for open systems interconnection

OSI Security Architecture(X.800 – Security for Open Systems Interconnection)

  • International Standard

  • 5 Categories

  • 14 Services


Osi security architecture categories services

OSI Security Architecture Categories(services)

  • Authentication (peer-entity, data-origin)

  • Access Control

  • Data Confidentiality (connection,

  • connectionless, selective-field, traffic-flow)

  • Data Integrity (connection[recovery,

  • no-recovery, selective-field],

  • connectionless[no-recovery,selective-field])

  • NonRepudiation (origin, destination)


Osi security architecture authentication

OSI Security ArchitectureAuthentication

Data Origin (m not protected)

A(m) m B

B(m,A)  AUTHENTIC(A)?

Peer Entity

A c B

S(A,B)  AUTHENTIC(A,B)?

S(c,masquerador,replay)  SECURE(c)?


Osi security architecture access control

Access REQUEST:

A(m) m {Host/System}

Host MATCHES m to A:

{Host/System}(m,A) m’ A

A GRANTED read/write access:

c

A(m’)  {Host/System}

OSI Security ArchitectureAccess Control


Osi security architecture confidentiality

CONNECTION:

cK

A  B (e.g. TCP)

CONNECTIONLESS:

A mK B

SELECTIVE-FIELD:

cK|c’

A  B

TRAFFIC-FLOW:

A {} B

OSI Security ArchitectureConfidentiality


Osi security architecture integrity

CONNECTION-RECOVERY:

c modification/destruction

A m B(m) recover  m

CONNECTION-NO RECOVERY:

c modification/destruction

A m B(m) detect  !!

SELECTIVE FIELD:

c modification/destruction

A m|m’ B(m) detect(m)  !!

OSI Security ArchitectureIntegrity


Osi security architecture non repudiation

OSI Security ArchitectureNon-Repudiation

SENDER VERIFICATION:

A m,[A] B(m,[A])  mA

RECEIVER VERIFICATION:

A m B

B [m],[B] A([m],[B])  mB


Osi security architecture availability

OSI Security ArchitectureAvailability

  • Upon request

  • Denial of Service

  • Attack Countermeasures:

  • Authentication

  • Encryption

  • Physical Response


Security mechanisms x 800 specific

  • Encipherment – unintelligible

  • Signature – data tag to ensure

  • a) Source b) Integrity c) anti-forgery

  • Access Control

  • Data Integrity

  • Authentication

  • Traffic Padding – prevent traffic analysis

  • Routing Control – adapt upon partial failure

  • Notarization – trusted third party

SECURITY MECHANISMS(X.800) - specific


Security mechanisms x 800 pervasive

  • Trusted Functionality

  • Security Label

  • Event Detection

  • Audit Trail

  • Recovery

SECURITY MECHANISMS(X.800) - pervasive


Attacks

  • PASSIVE:

  • System unaltered,

  • – hard to detect, easier to prevent

  • ACTIVE:

  • System altered,

  • – easier to detect, hard to prevent

ATTACKS


Attacks1

  • PASSIVE:

  • eavesdropping, monitoring,

  • message release, traffic analysis

  • ACTIVE:

  • replay,masquerade(impersonation),

  • modification, denial of service(supression,overload)

ATTACKS


Model for network security

Model for Network Security

Block Ciphers


Model for network access security

Model for Network Access Security

  • Gatekeeper: password-based login, screening logic

  • Internal controls: monitor activity, analyse stored info

Block Ciphers


  • Login