Introduction toNetwork Systems Security
Mort Anvari
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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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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
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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?
m
Internet
x y
?
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Message Loss Adversary A can discard m in its
transit
m
x y
A
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Message Interception Adversary A can get a copy of m
when m passes by
m
x y
m
m
A
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Message Modification Adversary A can arbitrarily modify
the content of m to become m’
m
x y
m’
A
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Message Insertion Adversary A can arbitrarily fabricate a
message m, pretending that m was sent by x
x y
m
src: xdst: yA
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Message Replay Adversary A can replay a message m
that has been sent earlier by x and received by y
x y
m
m
A
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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
x y
m… … … … ……
?????
A
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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 don’t 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… Protect messages from
interception 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 Adversary’s location hard to
determine New attacks keep emerging Cryptographic overhead
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Next Class Formal specification and
verification of network protocols Network security tools to counter
the effects of adversary actions