Transcript Summary of TCP/IP layers security

CSCE 813
Midterm Topics Overview
Internet Security - Farkas
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Network Attacks

Classifications
– Passive vs. Active
– Against security objectives
 What are the security objectives?
– Attacker’s activities
 Give some examples
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Forward Secrecy

Compromised 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
Why PFS is important for security protocols?
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Protection

Protection at storage
 Protection during usage
 Protection during transmission

Give an example attack and consequences for
each
 What are the basic security technologies?
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Communication Security
Security Protocols

Cryptographic protocols
 Services: 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 –
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


What is
How can we support
– Non-interference
– Non-interference
– Message confidentiality
– Message confidentiality
– Sender authentication
– Sender authentication
– Message authentication
– Message authentication
– Message integrity
– Message integrity
– Replay protection
– Replay protection
– …?
– …?
Why do we need protocol analysis?
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Attacks

Known 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 Stack
How does the TCP/IP stack
compares to the ISO-OSI model?
Application Layer
Why is layering a good idea?
Transport Layer
Internetwork Layer
How does layering impact the
security capabilities?
Network Access Layer What are the main protocols for
each layer?
How do these protocols
support security?
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What are the main security
capabilities supported by the
security protocols?
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Security -- At What Layer?

Where to implement security?
 Basic services that need to be implemented:
 Key management
 Confidentiality
 Nonrepudiation
 Integrity/authentication
 Authorization
 What are the security technologies supporting
these services?
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Network Access Layer

Application Layer
Transport Layer
Network Layer
Network Access L
Responsible for
packet transmission
on the physical media
 Protocols: Ethernet,
Token Ring,
Asynchronous
Transfer Mode
(ATM)
How does Ethernet support security?
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Virtual 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 Protocol
Service 1
Client 2
Client 1

LAC
Control
Session 1 (Call ID 1)
Session 2 (Call ID 2)
LNS
Service 2
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?
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L2TP and IPSec

L2TP is NOT secure without the support of
IPSec
 What are the attacks to consider?
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TCP/IP Protocol Stack

Application Layer
Transport Layer
Network Layer
Packaging
 Addressing
 Routing
What are the supported
security protocols?
Data Link Layer
What is the effect of
standardization on
security?
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Internet Engineering Task
Force 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 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 Architecture
IPsec module 1
IPsec module 2
SPD
SAD
SPD
IKE
IKE
IPsec
IPsec
SAD
SA
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The 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/readingroom/whitepapers/dns/security-issues-dns-1069
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Transport Layer

Application Layer
Host-to-host
transportation of packets
 Services:
– Connection-oriented or
Transport Layer
connectionless
– Reliable or unreliable
Network Layer

TCP, UDP
Data Link Layer
What are the TL
security protocols?
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Security Requirements
– Key management
What are the
advantages supporting
security at this layer?
– Confidentiality
– Repudiation
– Integrity/authentication
– Authorization
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Which are the most
popular transport layer
security protocols?
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Transport Layer Security
Protocols

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 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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Approaches

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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Cerberus
Third Party Authentication
1.Request ticketgranting ticket
2. Ticket +
session key
Client
3. Request servicegranting ticket
4. Ticket +
session key
6. Provide server
authentication
Kerberos
KDC
TGS
Once per
user logon
session
Once per
type of
service
5. Request service
Server
Once per
service
session
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Security-Enhanced Application
Protocol

Applications:
– Terminal access
– File transfer
– Electronic mail
– WWW transactions
– DNS
– Distributed file system
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SSH

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 Authentication
Sender A
KAprivate
M
H
Ks
E
E
c
KBpublic
Ks[M+H(M)]
M
E
c
KAprivate[H(M)]
KBpublic (Ks)
H
Compare
D
D
D
Ks
KBprivate
Receiver B
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KApublic
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Summary of Advantages and
Disadvantages of
Supporting Security at
Different Layers
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Network 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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Internetwork 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 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 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:
Web Application Security
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