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

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

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)  RSA Labs (de facto)

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 Low Impact   The loss could be expected to have a limited adverse effect on organizational operations, organizational assets, or individuals.   A limited adverse effect means that, for example, the loss of confidentiality, integrity, or availability might (i) cause a degradation in mission capability to an extent and duration that the organization is able to perform its primary functions, but the effectiveness of the functions is noticeably reduced; (ii) result in minor damage to organizational assets; (iii) result in minor financial loss; or (iv) result in minor harm to individuals.

10 Moderate Impact   The loss could be expected to have a serious adverse effect on organizational operations, organizational assets, or individuals.   A serious adverse effect means that, for example, the loss might (i) cause a significant degradation in mission capability to an extent and duration that the organization is able to perform its primary functions, but the effectiveness of the functions is significantly reduced; (ii) result in significant damage to organizational assets; (iii) result in significant financial loss; or (iv) result in significant harm to individuals that does not involve loss of life or serious, life-threatening injuries.

11 High Impact   The loss could be expected to have a severe or catastrophic adverse effect on organizational operations, organizational assets, or individuals.   A severe or catastrophic adverse effect means that, for example, the loss might (i) cause a severe degradation in or loss of mission capability to an extent and duration that the organization is not able to perform one or more of its primary functions; (ii) result in major damage to organizational assets; (iii) result in major financial loss; or (iv) result in severe or catastrophic harm to individuals involving loss of life or serious life threatening injuries.

12 Examples of Security Requirements  confidentiality – student grades  integrity – patient information  availability – authentication service  authenticity – admission ticket  non-repudiation – stock sell order

13 Computer Security Challenges 1. not simple – easy to get it wrong 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 a process, not an event 9. too often an after-thought 10. regarded as impediment to using system “Unusable security is not secure”

14 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

15 Aspects of Security  consider 3 aspects of information security: security attack security attack security mechanism (control) security mechanism (control) security service security service  note terms threat – a potential for violation of security threat – a potential for violation of security vulnerability – a way by which loss can happen vulnerability – a way by which loss can happen 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

16 Passive Attack - Interception

17 Passive Attack: Traffic Analysis Observe traffic pattern

18 Active Attack: Interruption Block delivery of message

19 Active Attack: Fabrication Fabricate message

20 Active Attack: Replay

21 Active Attack: Modification Modify message

22 Handling Attacks Passive attacks – focus on Prevention Passive attacks – focus on Prevention Easy to stopEasy to stop Hard to detectHard to detect Active attacks – focus on Detection and Recovery Active attacks – focus on Detection and Recovery Hard to stopHard to stop Easy to detectEasy to detect

23 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

24 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”

25 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

26 Security Mechanism  a.k.a. control  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

27 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

28 Model for Network Security

29  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

30 Model for Network Access Security

31  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  note that model does not include: 1. monitoring of system for successful penetration 2. monitoring of authorized users for misuse 3. audit logging for forensic uses, etc.

32 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