GENERAL DESCRIPTION OF THE SUBJECT: Security is a very important aspect of communication networks. By taking this subject, students understand the functioning and know how to use the main cryptographic tools to provide security to a network (symmetric and asymmetric cryptosystems, and public key infrastructure). These tools are used in the main secure communication protocols. The subject also explains what these protocols are, when and how they can be used. In addition, students learn about the risks of TCP/IP communications, the available vulnerability detection tools and how to use them, and how to configure a system to accept only one type of connections (firewall). Finally, the main intrusion detection tools and techniques for creating a deception system are covered. Students are able to design the security architecture of a computer system.