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Eyad Alshareef 1 Cryptography and Network Security - PowerPoint PPT Presentation


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Cryptography and Network Security. Introduction. The most critical phase of e-transactions is ensuring the security of e-payments and the privacy of the information Transaction contents can be read, modified, or made up by anyone. . Introduction.

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introduction
Introduction
  • The most critical phase of e-transactions is ensuring the security of e-payments and the privacy of the information
  • Transaction contents can be read, modified, or made up by anyone.

Eyad Alshareef

introduction3
Introduction
  • Internet security is not about protecting hardware or physical environment
  • It is about protecting information
  • Electronic security
    • Focuses on designing measures that can enforce security policies
    • When a malicious attack occurs

Eyad Alshareef

background
Background
  • Information Security requirements have changed in recent times
  • traditionally provided by physical and administrative mechanisms
  • computer use requires automated tools to protect files and other stored information
  • use of networks and communications links requires measures to protect data during transmission

Eyad Alshareef

definitions
Definitions
  • Computer Security - generic name for the collection of tools designed to protect data and to thwart hackers (in your computer)
  • Network Security - measures to protect data during their transmission
  • Internet Security - measures to protect data during their transmission over a collection of interconnected networks

Eyad Alshareef

the internet is an insecure place
The Internet Is An Insecure Place
  • Many protocols do not provide any security.
  • Viruses, worms, Trojan horses etc.
  • Client/server applications often require transmission of user identity/passwords.
  • “Hackers” may sniff passwords and other sensitive information of the network.
  • Need to restrict control access privileges
  • No system is totally immune to security problems.

Eyad Alshareef

solution
Solution?
  • There is nothing more secure then a computer which is not connected to the network – and powered off!
  • But…
  • These restrictions are simply unrealistic and unacceptable.

Eyad Alshareef

what we want from security
What we want from Security
  • Some characteristics we might like:
    • messages should be transmitted to destination
    • only the recipient should see it
    • only the recipient should get it
    • proof of the sender’s identity
    • message shouldn’t be corrupted in transit
    • message should be sent/received once only

Eyad Alshareef

services mechanisms attacks
Services, Mechanisms, Attacks
  • consider three aspects of information security:
    • security attack
    • security mechanism
    • security service
  • consider in reverse order

Eyad Alshareef

security service
Security Service
  • is something that enhances the security of the data processing systems and the information transfers of an organization
  • intended to counter security attacks
  • make use of one or more security mechanisms to provide the service
  • replicate functions normally associated with physical documents
    • eg have signatures, dates; need protection from disclosure, tampering, or destruction; be notarized or witnessed; be recorded or licensed

Eyad Alshareef

security mechanism
Security Mechanism
  • a mechanism that is designed to detect, prevent, or recover from a security attack
  • no single mechanism that will support all functions required
  • however one particular element underlies many of the security mechanisms in use: cryptographic techniques
  • hence our focus on this area

Eyad Alshareef

security attack
Security Attack
  • any action that compromises the security of information owned by an organization
  • information security is about how to prevent attacks, or failing that, to detect attacks on information-based systems
  • have a wide range of attacks
  • can focus of generic types of attacks
  • note: often threat & attack mean same

Eyad Alshareef

attacks services and mechanisms
Attacks, Services and Mechanisms
  • Security Attack:Any action that compromises the security of information.
  • Security Mechanism:A mechanism that is designed to detect, prevent, or recover from a security attack.
  • Security Service:A service that enhances the security of data processing systems and information transfers. A security service makes use of one or more security mechanisms.

Eyad Alshareef

what functionality is needed
What Functionality Is Needed?
  • Authentication -- who user is
  • Authorization -- who is allowed to do what
  • Enforcement -- make sure people do what they are supposed to do

Eyad Alshareef

methods
Methods
  • Cryptography
    • Converting messages to unreadable forms...

and then converting it back to the readable form

  • Steganography
    • Hiding the existence of a message

Eyad Alshareef

steganography

Steganography

Eyad Alshareef

steganography17
Steganography
  • Used for concealing information inside other information
  • Some techniques:
    • Character marking: selected letter of printed or typewritten text are overwritten in pencil
    • Invisible ink
    • Pin punctures: small pin punctures are only shown if paper is hold against a light source
    • Typewriter correction ribbon: used between lines of normal black ribbon. Only visible under strong light.

Eyad Alshareef

null cipher
Null Cipher

Fishing freshwater bends and saltwater coasts rewards anyone feeling stressed. Resourceful anglers usually find masterful leapers fun and admit swordfish rank overwhelming anyday.

Send lawyers, guns, and money.

Eyad Alshareef

invisible ink
Invisible Ink
  • Write with lemon juice and a toothpick/ cotton swab. Let the paper dry.
  • Heat the paper with an iron to reveal the hidden message.

Eyad Alshareef

introduction to security
Introduction to Security
  • Businesses are increasingly dependent on information and communication technology
  • security is becoming a primary concern with public access systems
  • there are different types of attack:
    • viruses
    • unauthorised access
    • hacking

Eyad Alshareef

what can go wrong
What Can Go Wrong…
  • …when your computer y receive or is waiting for a message m?

?

Internet

m

x

y

Eyad Alshareef

message loss
Message Loss
  • Adversary A can discard m in its transit

A

m

x

y

Eyad Alshareef

message interception
Message Interception
  • Adversary A can get a copy of m when m passes by

m

A

m

m

x

y

Eyad Alshareef

message modification
Message Modification
  • Adversary A can arbitrarily modify the content of m to become m’

A

m

m’

x

y

Eyad Alshareef

message insertion
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

Eyad Alshareef

message replay
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

Eyad Alshareef

denial of service attack

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

Eyad Alshareef

network security is great
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

Eyad Alshareef

types of security threats
Types of Security Threats
  • Normal flow
  • Interruption
  • Interception
  • Modification
  • Fabrication

Eyad Alshareef

security attacks
Security Attacks

Eyad Alshareef

what is network security
What is network security?

Confidentiality: only sender, intended receiver should “understand” message contents

  • sender encrypts message
  • receiver decrypts message

Authentication: sender, receiver want to confirm identity of each other

Message Integrity: sender, receiver want to ensure message not altered (in transit, or afterwards) without detection

Access and Availability: services must be accessible and available to users

Eyad Alshareef

security attacks32
Security Attacks
  • Interruption: This is an attack on availability
  • Interception: This is an attack on confidentiality
  • Modfication: This is an attack on integtrity
  • Fabrication: This is an attack on authenticity

Eyad Alshareef

security criteria
Security Criteria

Eyad Alshareef

friends and enemies alice bob trudy
Friends and enemies: Alice, Bob, Trudy
  • well-known in network security world
  • Bob, Alice (lovers!) want to communicate “securely”
  • Trudy (intruder) may intercept, delete, add messages

Alice

Bob

data, control messages

channel

secure

sender

secure

receiver

data

data

Trudy

Eyad Alshareef

a model for network security

TTP

A

P

P

A Model for Network Security
  • Security techniques commonly have three components:
    • security related transformation of message
    • secret keys shared by the participants
    • need for third party notary support for some transactions

Eyad Alshareef

firewalls
Firewalls
  • can be an effective means of protecting a system or network from network-based security threats
  • while providing access to the outside world
  • positioned between the system(s) and the outside world
  • all external traffic must pass through it
  • a single choke point where security measures can be concentrated

Eyad Alshareef

types of firewall
Types of Firewall
  • there are hardware and software firewalls
  • can be implemented on a designated gateway or dedicated machine
  • there are three types:
    • packet filtering routers
    • application-level gateway
    • circuit-level gateway

Eyad Alshareef

packet filtering routers
Packet Filtering Routers
  • A router that applies a set of rules to incoming and outgoing packets:
    • based on fields in the IP and transport header
    • e.g. source, destination IP, port and IP protocol
    • where no rule exists to discard of forward

Eyad Alshareef

application level gateway
Application-Level Gateway
  • An application-level gateway acts as a relay of application-level traffic
  • also known as a proxy server
  • users contact the proxy using TCP/IP based applications
  • the gateway checks and forwards for supported/allowed applications or safe sub-sets/features thereof
  • these tend to be more secure than packet filters
  • disadvantage: processing overhead

Eyad Alshareef

circuit level gateway
Circuit-level Gateway
  • Can be stand-alone system or hosted
  • does not permit end-to-end TCP connection
  • sets up two TCP connection one on either side
  • TCP segments are relayed without examining content
  • based on the principle of allowing connections only to select/trusted hosts
  • usually used for outgoing connections
  • can therefore complement application-layer gateways for incoming traffic

Eyad Alshareef

security services x 800
Security Services (X.800)
  • Authentication - assurance that the communicating entity is the one claimed
  • Access Control - prevention of the unauthorized use of a resource
  • Data Confidentiality –protection of data from unauthorized disclosure
  • Data Integrity - assurance that data received is as sent by an authorized entity
  • Non-Repudiation - protection against denial by one of the parties in a communication

Eyad Alshareef

classify security attacks as
Classify Security Attacks as
  • passive attacks - eavesdropping on, or monitoring of, transmissions to:
    • obtain message contents, or
    • monitor traffic flows
  • active attacks – modification of data stream to:
    • masquerade of one entity as some other
    • replay previous messages
    • modify messages in transit
    • denial of service

Eyad Alshareef

model for network security45
Model for Network Security
  • using this model requires us to:
    • design a suitable algorithm for the security transformation
    • generate the secret information (keys) used by the algorithm
    • develop methods to distribute and share the secret information
    • specify a protocol enabling the principals to use the transformation and secret information for a security service

Eyad Alshareef

model for network access security47
Model for Network Access Security
  • using this model requires us to:
    • select appropriate gatekeeper functions to identify users
    • implement security controls to ensure only authorised users access designated information or resources
  • trusted computer systems can be used to implement this model

Eyad Alshareef

more information
More Information
  • Spyware
    • Software the user unknowingly installs through an email attachment or downloading an effected file that could be used for illicit reasons
    • Usually used to collect information from infected computer

Eyad Alshareef

more information49
More Information
  • Adware
    • Software that sneaks into user hard disk
    • Installed by internet advertising companies tp promote pop-up ads and release information for advertisers on the outside

Eyad Alshareef

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