1. Lecture 1 Introduction Dr. nermin hamza 1

2. Aim of Course Overview Cryptography Symmetric and Asymmetric Key management Researches topics 2

3. Resources Lectures Some notes Cryptography and Network Security “principles and practice 5 th edition William Stallings 3

4. http://elearning.issr.cu.edu.eg/ 4

5. OVERVIEW Confidentiality : The concept of Confidentiality in information security pertains to the protection of information and prevention of unauthorized access or disclosure. Integrity : deals with prevention of unauthorized modification of intentional or accidental modification. 5

6. Definitions Computer Security - generic name for the collection of tools designed to protect data and to thwart hackers Network Security - measures to protect data during their transmission Internet Security - measures to protect data during their transmission over a collection of interconnected networks 6

7. The Security Trinity 7

8. Prevention : to provide some level of security, it is necessary to implement measures to avoid the exploitation of vulnerabilities. Detection: procedures need to be put in place to discover potential problems or security breaches. Response: Organizations need to develop a plan that identifies what is need to be protected 8

9. OSI Security Architecture ITU-T X.800 “Security Architecture for OSI” defines a systematic way of defining and providing security requirements 9

10. Aspects of Security consider 3 aspects of information security: The OSI Security Architecture ◦ Security Attack: Any action that compromise the security of information owned by an organization. ◦ Security Mechanism: A process that is designed to detect, prevent or recover from a security attack. ◦ Security Services: Security Services is the services to implement security policies and implemented by security mechanism 10

11. 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 can focus of generic types of attacks 11

12. Security Attack  Threats تهديد mean anything that can interrupt the operation, functioning, integrity, or availability of a network or system, these can take any forms.  Vulnerabilities ثغره are inherent weakness in the design, configuration, implementation, or management of the network or the system that renders it to be susceptible to threats.  Attacks هجوم are a specific technique used to exploit the vulnerabilities 12

13. Security Attacks General Categories ◦ Outside and Inside attack ◦ Passive attack and active attack Functionality of attacks ◦ Interruption, Modification, Interception... Types of attacks ◦ Replay Attack, Intrusion Attacks 13

14. General Attacks 14

15. Passive Attacks 15

16. Example: Release of message contents 16

17. Passive Attacks Release of message contents A telephone conversation, an E-mail messages, and file transfer can be easily accessed without effecting the message. Traffic analysis To observe pattern of messages from sender and receiver. 17

18. Active Attacks 18

19. Active Attacks  Replay Attack: A hacker executes a replay attack by intercepting and storing a legitimate transmission between two systems and retransmitting it at a later time.  Denial-of-Service (DoS) Attacks: attempt to exhaust the network or server resources in order to render it useless for legitimate hosts and users.  Masquerading server attack in which an attacker pretends to be as a legal server by creating a valid responding message from an eavesdropped communication between the remote server S and a user A 19

20. Active Attacks Modification هجوم يعدل على محتوى الرسالة : An unauthorized party does not only gain access to the asset, but also tampers it. This is an attack that violates integrity. Examples include value manipulation in the date file, and modifying the content of messages being transmitted in a network. Fabrication لهجوم المزور أو المفبرك : An unauthorized party installing a malicious object or program on the system. This is an attack that violates authenticity. Examples include the insertion of spurious messages in a network or the addition of records to a file. 20

21. Security Service ◦ enhance security of data processing systems and information transfers of an organization ◦ intended to counter security attacks ◦ using one or more security mechanisms ◦ often replicates functions normally associated with physical documents  which, for example, have signatures, dates; need protection from disclosure, tampering, or destruction; be notarized or witnessed; be recorded or licensed 21

22. Security Services X.800: “a service provided by a protocol layer of communicating open systems, which ensures adequate security of the systems or of data transfers” A processing or communication service that enhances the security of data processing systems and the information transfers of an organization of 22

23.  Authentication ◦ Concerned with assuring that a communication is authentic.  Confidentiality : ◦ Preventing the sensitive information from unauthorized user.  Integrity : ◦ Preventing the information from modification by unauthorized users.  Availability: ◦ Assuring that the authorized users have timely access to the information in the system and to the network.  Access Control: ◦ Ability to limit and control the access to the host systems and applications via communication links.  Non-repudiation: ◦ Preventing either sender or receiver from denying a transmitted message. 23 Security Services:

24. Security Mechanism A process that is designed to detect, prevent or recover from a security attack no single mechanism that will support all services required however one particular element underlies many of the security mechanisms in use: ◦ cryptographic techniques 24

25. Security Mechanisms - Digital Signature Data appended to a data unit that allows a recipient of data unit to prove the source and integrity of the data unit. - Authentication Exchange A mechanism intended to ensure the identity of an entity by means of information exchange - Encipherment The use of mathematical algorithms tp transform data into a form that is not readily intelligible. 25

26. Security Mechanisms - Notarization The use of a trusted third party to assure certain properties of ad data exchange - Traffic Padding The insertion of bits into gaps in a data stream to frustrate traffic analysis attempts. - Routing Control Enables selection of particular physically secure routes for certain data and allows routing changes especially when a breach of security is suspected 26

27. Introduction (cont’d) Relation between Security and Mechanisms : 27 EnciphermentDigital Signature Access control Authentication exchange ConfidentialityY Data integrityYY AvailabilityY AuthenticationYYY NonrepudationY

28. Model for Network Security 28

29. Model for Network Security using this model requires us to: 1.design a suitable algorithm for the security transformation 2.generate the secret information (keys) used by the algorithm 3.develop methods to distribute and share the secret information 4.specify a protocol enabling the principals to use the transformation and secret information for a security service 29

30. Model for Network Access Security 30

31. Model for Network Access Security using this model requires us to: 1.select appropriate gatekeeper functions to identify users 2.implement security controls to ensure only authorised users access designated information or resources trusted computer systems may be useful to help implement this model 31