Network Security and
Cryptography
Lecture 1: Introduction to Cryptography
Presented By: Kamaljeet Kaur
Faculty of Computer Science and Engineering
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Unit 1 Syllabus
• Introduction to Cryptography, Security Threats, Vulnerability,
Active and Passive attacks, Security services and mechanism,
Conventional Encryption Model, CIA model
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Content:
• Computer security
• Cryptography
• Vulnerability
• Security Threats
• OSI security Architecture
• Security Attacks
• Security services
• Security Mechanisms
• CIA Model
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Computer Security
• Is the protection of computer systems and information from
harm, theft and unauthorized use.
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Introduction to Cryptography
• The term is derived from the Greek word kryptos
• Study of secure communications techniques
• Allow only the sender and intended recipient to view content
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Vulnerability
• a weakness or opportunity that can exploit and gain
unauthorized access to a computer system
• Types:
• Network vulnerability
• OS vulnerability
• Process vulnerability
• Human vulnerability
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Malicious Code
• Virus
• Worms
• Trojan Horse
• Spyware
• Adware
• Keylogger
• Ransomware
• Backdoor (Remote Access Trojan)
• Example: Zeus, Mydoom, Stuxnet
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OSI Security Architecture
• Focuses on security attacks, mechanisms, and services.
• Security attack: action that compromises the security
• Two types of security attacks
a) Passive attack
b) active attack
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Passive Attack
• To make use of informati on but does not affect resources.
• Two types of passive attacks are:
• Release of message contents and
• Traffi c analysis.
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Release of message contents
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Traffic Analysis
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Active Attack
• Involve some modification of the data stream or a false stream
• Subdivided into four categories:
• Masquerade
• Replay
• Modification of messages
• Denial of service
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Masquerade
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Replay
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Modification of data
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Denial of Service
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Security Services
• Enhances the security of system and information transfer .
• Categories:
• Authentication
• Access control
• Data confidentiality
• Data integrity
• Nonrepudiation
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Security Mechanisms
• It is designed to detect, prevent or recover from a security attack.
• It is a tool or technique used to implement security services.
• Some mechanisms are:
• Encipherment
• Access control
• Notarization
• Data integrity
• Authentication exchange
• Digital signature
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Techniques for providing Security
• A security related transformation on the information to be sent
• Secret information transmitted without knowing to opponent
• Conventional encryption Model
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Model for Network Security
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CIA Model
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Queries?????
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