Cryptography and Network SecurityChapter 1 – IntroductionBackgroundDefinitionsAim of CourseInformation securitySecurity ‘components’Services, Mechanisms, AttacksSecurity ServiceSecurity MechanismSecurity AttackSecurity AttacksOSI Security ArchitectureSecurity ServicesSecurity Services (X.800)Security Mechanisms (X.800)Classify Security Attacks asPassive? Active?Model (#1) for Network SecurityModel for Network SecurityModel (#2) for Network Access SecurityModel for Network Access SecuritySummaryCryptography and Network Security2nd Editionby William StallingsNote:Lecture slides by Lawrie Brown and Henric Johnson,Modified by Andrew YangNetwork Security 2Chapter 1 – IntroductionThe 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 TzuNetwork Security 3Background•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 transmissionNetwork Security 4Definitions•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 networksNetwork Security 5Aim of Course•our focus is on Internet Security•consists of measures to deter, prevent, detect, and correct security violations that involve the transmission of informationNetwork Security 6Information security•Assets•Threats•Attacks •Vulnerabilities•ControlsNetwork Security 7Security ‘components’•Also known as security goals, objectives, etc.1. Confidentiality2. Data integrity3. Origin integrity (aka. Authenticity)4. Non-repudiability5. AvailabilityNetwork Security 8Services, Mechanisms, Attacks•need systematic way to define requirements•consider three aspects of information security:–security attack–security mechanism–security serviceNetwork Security 9Security 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 licensedNetwork Security 10Security Mechanism•a mechanism that is designed to detect, prevent, or recover from a security attack•no single mechanism will support all functions required•however one particular element underlies many of the security mechanisms in use: cryptographic techniquesNetwork Security 11Security 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 sameNetwork Security 12Security AttacksSecurity AttacksNetwork Security 13OSI Security Architecture•ITU-T X.800 Security Architecture for OSIlocal copy•defines a systematic way of defining and providing security requirements•provides a useful, although abstract, overview of network security conceptsNetwork Security 14Security Services•RFC 2828 (Internet Security Glossary) defines it as: a processing or communication service provided by a system to give a specific kind of protection to system resources X.800 defines it as: a service provided by a protocol layer of communicating open systems, which ensures adequate security of the systems or of data transfers•X.800 defines it in 5 major categoriesNetwork Security 15Security Services (X.800)•Authentication - assurance that the communicating entity is the one claimed•Access Control - prevention of 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 communicationNetwork Security 16Security Mechanisms (X.800)•pervasive security mechanisms:–trusted functionality, security labels, event detection, security audit trails, security recovery•specific security mechanisms:–encipherment, digital signatures, access controls, data integrity, authentication exchange, traffic padding, routing control, notarizationNetwork Security 17Classify Security Attacks as•passive attacks (fig. 1) - eavesdropping on, or monitoring of, transmissions to:–obtain message contents, or–monitor traffic flows•active attacks (fig. 2a, 2b)– modification of data stream to:–masquerade of one entity as some other–replay previous messages–modify messages in transit–denial of serviceNetwork Security 18Passive? Active?Passive? Active?Network Security 19Model (#1) for Network SecurityNetwork Security 20Model 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 serviceNetwork Security 21Model (#2) for Network Access SecurityNetwork Security 22Model 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 (aka. bastion hosts) can be used to implement this modelNetwork Security 23Summary•have considered:–computer, network, internet security def’s–security services, mechanisms, attacks–X.800 standard–models for network (access)