Cryptography and Network Security Overview & Chapter 1 Fifth Edition by William Stallings Lecture slides by Lawrie Brown.

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1 Cryptography and Network Security Overview & Chapter 1 Fifth Edition by William Stallings Lecture slides by Lawrie Brown

2 Chapter 0 – Reader’s Guide The art of war teaches us to rely not on the likelihood of the enemy's not coming, but on our own readiness to receive him; not on the chance of his not attacking, but rather on the fact that we have made our position unassailable. —The Art of War, Sun Tzu

3 Roadmap  Cryptographic algorithms symmetric ciphers symmetric ciphers asymmetric encryption asymmetric encryption hash functions hash functions  Mutual Trust  Network Security  Computer Security

4 Standards Organizations  National Institute of Standards & Technology (NIST)  Internet Society (ISOC)  International Telecommunication Union Telecommunication Standardization Sector (ITU-T)  International Organization for Standardization (ISO)

5 Chapter 1 – Introduction  The combination of space, time, and strength that must be considered as the basic elements of this theory of defense makes this a fairly complicated matter. Consequently, it is not easy to find a fixed point of departure.. — On War, Carl Von Clausewitz

6 Computer Security  the protection afforded to an automated information system in order to attain the applicable objectives of preserving the integrity, availability and confidentiality of information system resources (includes hardware, software, firmware, information/data, and telecommunications)

7 Key Security Concepts

8 Levels of Impact  can define 3 levels of impact from a security breach Low Low Moderate Moderate High High

9 Examples of Security Requirements  confidentiality – student grades  integrity – patient information  availability – authentication service

10 Computer Security Challenges 1. not simple 2. must consider potential attacks 3. procedures used counter-intuitive 4. involve algorithms and secret info 5. must decide where to deploy mechanisms 6. battle of wits between attacker / admin 7. not perceived on benefit until fails 8. requires regular monitoring 9. too often an after-thought 10. regarded as impediment to using system

11 OSI Security Architecture  ITU-T X.800 “Security Architecture for OSI”  defines a systematic way of defining and providing security requirements  for us it provides a useful, if abstract, overview of concepts we will study

12 Aspects of Security  consider 3 aspects of information security: security attack security attack security mechanism security mechanism security service security service  note terms threat – a potential for violation of security threat – a potential for violation of security attack – an assault on system security, a deliberate attempt to evade security services attack – an assault on system security, a deliberate attempt to evade security services

13 Passive Attacks

14 Active Attacks

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

16 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”  RFC 2828: “a processing or communication service provided by a system to give a specific kind of protection to system resources”

17 Security Services (X.800)  Authentication - assurance that communicating entity is the one claimed have both peer-entity & data origin authentication have both peer-entity & data origin authentication  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  Availability – resource accessible/usable

18 Security Mechanism  feature 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 cryptographic techniques  hence our focus on this topic

19 Security Mechanisms (X.800)  specific security mechanisms: encipherment, digital signatures, access controls, data integrity, authentication exchange, traffic padding, routing control, notarization encipherment, digital signatures, access controls, data integrity, authentication exchange, traffic padding, routing control, notarization  pervasive security mechanisms: trusted functionality, security labels, event detection, security audit trails, security recovery trusted functionality, security labels, event detection, security audit trails, security recovery

20 Model for Network Security

21  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

22 Model for Network Access Security

23  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

24 Summary  topic roadmap & standards organizations  security concepts: confidentiality, integrity, availability confidentiality, integrity, availability  X.800 security architecture  security attacks, services, mechanisms  models for network (access) security