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