CSCE 790: Computer Network Security

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CSCE 790Computer Network Security

• Chin-Tser Huang
• huangct_at_cse.sc.edu
• University of South Carolina

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About Me

• Chin-Tser Huang
• Ph.D. in Computer Sciences, 2003, University of
  Texas at Austin
• My first semester with USC
• Research in network security, network protocol
  design and verification, distributed systems
• My new web page is not ready, but if you want to
  know more about me, here is the old one
  http//www.cs.utexas.edu/users/chuang

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About the Course

• A grad-level seminar course focusing on basics
  and issues in network security
• First half will be lectures about elements of
  network security, cryptography backgrounds, and
  introduction to network security designs
• Second half will be your chance to present what
  you have learned from key research papers

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Course Information Online

• http//www.cse.sc.edu/huangct/CSCE790F03/index.ht
  m
• List of assigned paper and useful links will be
  added shortly
• Lecture slides will be available online too

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Your Best Strategy

• Come to every lecture to learn basic security
  problems and skills to counter them
• Keep yourself exposed to articles related to
  network security to collect project ideas
• Read each assigned paper and write good summary
  for each paper
• Do not wait till last minute to prepare for exam
  or work on project
• Enjoy the fun!

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What Can Go Wrong

• when your computer y receive or is waiting for a
  message m?

?
Internet
m
x
y
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Message Loss

• Adversary A can discard m in its transit

A
m
x
y
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Message Interception

• Adversary A can get a copy of m when m passes by

m
A
m
m
x
y
9
Message Modification

• Adversary A can arbitrarily modify the content of
  m to become m

A
m
m
x
y
10
Message Insertion

• Adversary A can arbitrarily fabricate a message
  m, pretending that m was sent by x

src x dst y
A
m
x
y
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Message Replay

• Adversary A can replay a message m that has been
  sent earlier by x and received by y

m
A
m
x
y
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Denial-of-Service Attack

• Adversary A can send huge amount of messages to y
  to block m from arriving at y

A
m
?????
x
y
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Type of Attacks

• Passive attacks
• Traffic analysis
• Message interception

• Active attacks
• Message loss
• Message modification
• Message insertion
• Message replay
• Denial-of-Service attack

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Network Security Services

• Confidentiality
• Integrity
• Authentication
• Anti-replay

• Availability
• Access control
• Non-repudiation
• Anonymity

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Confidentiality

• Keep message known only to the receiver and
  secret to anyone else
• Counter message interception

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Integrity

• When receiver receives message m, receiver can
  verify m is intact after sent by sender
• Counter message modification

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Authentication

• When receiver receives message m, receiver can
  verify m is indeed sent by the sender recorded in
  m
• Counter message insertion

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Anti-replay

• When receiver receives message m, receiver can
  verify m is not a message that was sent and
  received before
• Counter message replay

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Availability

• Property of a system or a resource being
  accessible and usable upon demand by an
  authorized entity
• Counter denial-of-service attack

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Access Control

• Mechanism to enforce access rights to resources
  and data
• Users can access resources and data to which they
  have access rights
• Users cannot access resources and data to which
  they dont have access rights

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Non-repudiation

• When receiver receives message m, receiver gets
  proof that sender of m ever sent m
• Receiver of m can show proof to third-party so
  that sender of m cannot repudiate

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Anonymity

• Identity of sender is hidden from receiver
• When receiver receives message m, receiver has no
  clue about sender of m

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Network Security Is Great

• Prevent messages from being attacked in their
  transit
• Detect and discard messages that are modified,
  inserted, or replayed
• Disallow unauthorized access to local system
  resource and sensitive data

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But Hard To Achieve

• Many layers in network architecture
• Many different media of network connection
• Adversarys location hard to determine
• New attacks keep emerging
• Cryptographic overhead

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Why Should You Take This Course

• Security is an increasingly important issue
• You want to have basic knowledge about network
  security
• You can learn latest attacks and newest skills to
  counter those attacks
• You have a chance to implement the skills learned
  in the class