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CSCE 813CSCE 813 Midterm Topics Overview Midterm Topics Overview

Network AttacksNetwork Attacks

Classifications– Passive vs. Active– Against security objectives

What are the security objectives?

– Attacker’s activities Give some examples

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Forward SecrecyForward SecrecyCompromised key: permits the disclosure of

the data encrypted by the compromised key. No additional keys can be generated from

the compromised key. Perfect Forward Secrecy: compromise of a

single key will permit access to only data protected by a single key

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Why PFS is important for security protocols?

ProtectionProtection

Protection at storageProtection during usageProtection during transmission

Give an example attack and consequences for each

What are the basic security technologies?

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Communication Security Communication Security Security ProtocolsSecurity Protocols

Cryptographic protocolsServices: secrecy, integrity, authentication,

key exchange, non-repudiation, etc.Components: communicating parties

(nodes), trusted third party, encryption algorithms, hash functions, timestamps, nonce, etc.

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Security Properties – Security Properties – Authentication of Origin Authentication of Origin

Verify – Who sent the message?– Who sent the message to whom?– Who sent the message to whom and how many

times?

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Security Properties Security Properties What is

– Non-interference– Message confidentiality– Sender authentication– Message authentication– Message integrity– Replay protection– …?

How can we support– Non-interference– Message confidentiality– Sender authentication– Message authentication– Message integrity– Replay protection– …?

Why do we need protocol analysis?

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AttacksAttacksKnown attacks

– Can be picked up by careful inspection

Non-intuitive attacks– Not easily apparent– May not depend on flaws or weaknesses of

cryptographic algs. – Use variety of methods, e.g., statistical analysis,

subtle properties of crypto algs., etc.

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TCP/IP Protocol StackTCP/IP Protocol Stack

Application Layer

Transport Layer

Internetwork Layer

Network Access Layer

How does the TCP/IP stack compares to the ISO-OSI model?

Why is layering a good idea?

How does layering impact the security capabilities?

What are the main protocols for each layer?

How do these protocols support security?

What are the main security What are the main security capabilities supported by the capabilities supported by the

security protocols? security protocols?

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Security -- At What Security -- At What LayerLayer??

Where to implement security? Basic services that need to be implemented:

Key managementConfidentialityNonrepudiationIntegrity/authenticationAuthorization

What are the security technologies supporting these services?

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Network AccessNetwork Access Layer Layer

Responsible for packet transmission on the physical media

Protocols: Ethernet, Token Ring, Asynchronous Transfer Mode (ATM)

How does Ethernet support security?

Application Layer

Transport Layer

Network Layer

Network Access L

Virtual Private NetworkVirtual Private Network

L2TP: combines Layer 2 Forwarding (L2F) and Point-to-Point Tunneling Protocol (PPTP)

What does tunneling mean? Who can create a tunnel?

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L2TP ProtocolL2TP Protocol

Tunnel components– Control channel (reliable): control sessions and tunnel– Data channel (unreliable): created for each call

What is the level of protection between Client 1 & LAC?LAC & LNS?

ControlSession 1 (Call ID 1)

Session 2 (Call ID 2)LAC LNSClient 1

Client 2Service 1

Service 2

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L2TP and IPSecL2TP and IPSecL2TP is NOT secure without the support of

IPSec What are the attacks to consider?

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TCP/IP Protocol StackTCP/IP Protocol Stack

Application Layer

Transport Layer

Network Layer

Data Link Layer

PackagingAddressingRouting

What are the supported security protocols?

What is the effect of standardization on security?

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Internet Engineering Task Internet Engineering Task Force StandardizationForce Standardization

IPv6 development requirements: Strong security features

1992: IPSEC WG (IETF)– Define security architecture – Standardize IP Security Protocol and Internet Key

Management Protocol 1998: revised version of IP Security Architecture

– IPsec protocols (two sub-protocols AH and ESP)– Internet Key Exchange (IKE)

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IP Security OverviewIP Security Overview

IPSec: method of protecting IP datagrams– Data origin authentication– Connectionless data integrity authentication– Data content confidentiality– Anti-replay protection– Limited traffic flow confidentiality

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IP Security ArchitectureIP Security ArchitectureIPsec module 1 IPsec module 2

SPD

SADSAD

SPD

IKE IKE

IPsec IPsecSA

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The Domain Name SystemThe Domain Name System

Why is it needed?Is this secure?What are the security concerns?

Good reading: SANS Institute: Security Issues with DNS, http://www.sans.org/reading-room/whitepapers/dns/security-issues-dns-1069

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Transport LayerTransport Layer Host-to-host

transportation of packets Services:

– Connection-oriented or connectionless

– Reliable or unreliable TCP, UDP

Application Layer

Transport Layer

Network Layer

Data Link LayerWhat are the TL security protocols?

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Security Security RequirementsRequirements

– Key management– Confidentiality– Repudiation– Integrity/authentication– Authorization

What are the advantages supporting security at this layer?

Which are the most popular transport layer security protocols?

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Transport Layer Security Transport Layer Security ProtocolsProtocols

Connectionless and connection-oriented transport layer service: Security Protocol 4 (SP4) – NSA, NIST, Transport Layer Security Protocol (TLSP) – ISO

Connection-oriented transport layer service:– Encrypted Session Manager (ESM) – AT&T Bell Labs.– Secure Socket Layer (SSL) – Netscape Communications– Transport Layer Security (TLS) – IETF TLS WG

Most popular transport layer security protocols

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Application LayerApplication Layer Provides applications that

can access services at the other layers, e.g., telnet (port 23), mail (port 25), finger (port 79)

New services and protocols are always being developed

Application Layer

Transport Layer

Network Layer

Data Link Layer

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ApproachesApproaches

Provide security system that can be used by different applications– Develop authentication and key distribution

models

Enhance application protocol with security features– Need to enhance each application

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Third Party AuthenticationThird Party Authentication

1.Request ticket- granting ticket

2. Ticket + session key

3. Request service- granting ticket

4. Ticket + session key

ClientKDC

TGS

Server

5. Request service6. Provide server authentication

Once peruser logonsession

Once perservicesession

Once pertype of service

Kerberos

Cerberus

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Security-Enhanced Application Security-Enhanced Application ProtocolProtocol

Applications:– Terminal access– File transfer– Electronic mail– WWW transactions– DNS– Distributed file system

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SSHSSH

Use generic transport layer security protocol over TCP/IP

Support for– Host and user authentication– Data compression– Data confidentiality– Integrity protection

Server listens for TCP connection on port 22, assigned to SSH

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PGP: Confidentiality and AuthenticationPGP: Confidentiality and Authentication

E

D

MH E

KAprivate

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KAprivate[H(M)]

ME

KsKB

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KBpublic (Ks)

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Compare

H

Sender A

Receiver B

Summary of Advantages and Summary of Advantages and Disadvantages ofDisadvantages of

Supporting Security at Supporting Security at Different LayersDifferent Layers

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Network Access Layer SecurityNetwork Access Layer Security

Dedicated link between hosts/routers hardware devices for encryption

Advantages: – Speed

Disadvantages:– Not scaleable– Works well only on dedicates links– Two hardware devices need to be physically connected

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InternInternetwork Layer Securityetwork Layer Security

IP Security (IPSec) Advantages:

– Overhead involved with key negotiation decreases <-- multiple protocols can share the same key management infrastructure

– Ability to build VPN and intranet Disadvantages:

– Difficult to handle low granularity security, e.g., nonrepudation, user-based security,

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Transport Layer SecurityTransport Layer Security

Advantages:– Does not require enhancement to each

application

Disadvantages:– Difficult to obtain user context– Implemented on an end system– Protocol specific implemented for each

protocol

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Application Layer SecurityApplication Layer Security Advantages:

– Executing in the context of the user --> easy access to user’s credentials

– Complete access to data --> easier to ensure nonrepudation– Application can be extended to provide security (do not depend on

the operating system)– Application understand data --> fine tune security

Disadvantages:– Implemented in end hosts– Security mechanisms have to be implemented for each application

--> – expensive– greated probability of making mistake

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Next Class: Next Class: Web Application SecurityWeb Application Security