cryptography and network security by behrouz a. forouzan pdf

Cryptography, a word with origin in Greek, means “secret writing.” We used the term to refer to the science and art of transforming messages to make them secure and immune to attacks. Access control uses methods to prove that a user has access right to the data or resources owned by a system. Notarization means selecting a third trusted party to control the communication between two entities. Routing control means selecting and continuously changing different available routes between the sender and the receiver to prevent the opponent from eavesdropping on a particular route. Traffic padding means inserting some bogus data into the data traffic to thwart the adversary’s attempt to use the traffic analysis.

c ew co m as In authentication exchange, two entities exchange some messages to prove their identity to each other. sh is s a Co re tud ur d v y se ia re so H er ur o. A digital signature is a means by which the sender can electronically sign the data and the receiver can electronically verify the signature. The checkvalue is created by a specific process from the data itself. The data integrity mechanism appends a short checkvalue to the data. encipherment, data integrity, digital signature, authentication exchange, traffic padding, routing control, notarization, and access control. Eight security mechanisms were discussed in this chapter. Access control provides protection against unauthorized access to data. Nonrepudiation protects against repudiation by either the sender or the receiver of the data. Authentication means to identify and authenticate the party at the other end of the line.

Data integrity is to protect data from modification, insertion, deletion, and replaying. Data confidentiality is to protect data from disclosure attack. We mentioned five security services: data confidentiality, data integrity, authentication, nonrepudiation, and access control. Examples of active attacks are modification, masquerading, replaying, repudiation, and denial of service. Attacks that threaten the integrity and availability are active attacks. An active attack may change the data or harm the system. Examples of passive attacks are snooping and traffic analysis. This means that the attack does not modify data or harm the system.

In a passive attack, the attacker’s goal is just to obtain information. Availability means that information needs to be available to authorized entities. Integrity means that changes to the information need to be done only by authorized entities. Confidentiality means protecting confidential information.

The three security goals are confidentiality, integrity, and availability. c ew co m as (Solution to Practice Set) Review Questions 1. CHAPTER 1 Introduction sh is s a Co re tud ur d v y se ia re so H er ur o.

Cryptography and network security by behrouz a. forouzan pdf