Textbook in PDF format

Today, the Internet has undoubtedly become the largest public data network that facilitates personal and business communications worldwide. The amount of traffic moving through the Internet as well as corporate networks is growing day by day. More and more people are communicating via emails, branch offices are using the Internet to remotely connect to their corporate networks and most com-mercial transactions such as shopping, bill payments and banking are also being done through the networks. Due to growing dependency of users, businesses and organizations on computer networks, it has become important to protect the information being exchanged from various security attacks. In addition, the confidentiality, authenticity and integrity of the messages moving across the networks must be ensured. This is where network security is important