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  • 1.  The OSI Security architecture• Security attacks• Security services• Security mechanism A model for network security
  • 2.  The OSI security architecture focuses on security attacks, mechanisms, and services. Security attack:Any action that compromises the security of information owned by an organization. Two types of security attacks a) Passive attack b) active attack
  • 3.  Passive attack attempts to learn or make use of information from the system but does not affect system resources. Two types of passive attacks are release of message contents and traffic analysis.
  • 4.  Active attacks involve some modification of the data stream or the creation of a false stream and can be subdivided into four categories : masquerade , replay, modification of messages, and denial of service.
  • 5.  X.800 defines it is the service provided by protocol layer of communicating open system which ensures adequate security of the systems or of data transfers. RFC 2828 defines as a communication service that is provided by a system to give a specific kind of protection to system resources;
  • 6.  Authentication Access control Data confidentiality Data integrity Nonrepudiation
  • 7.  Is a process that is designed to detect, prevent or recover from a security attack. Encipherment : It uses a mathematical algorithm to transfer the data into a form that can not be read by unauthorized user. Two types: Reversible encipherment Irreversible encipherment
  • 8.  A security-related transformation on the information to be sent. Some secret information shared by the two principals and, it is hoped, unknown to the opponent.