4. Cryptography, authentication, security protocols and VPNs

This technical section lists all the basic tools needed to develop technical solutions for exchanging data over different types of network (Internet, wireless). The basic tools include cryptography, defined as "the discipline including the principles, means and methods of transforming data in order to hide its content, prevent its modification from going undetected and/or prevent its unauthorized use" (ISO standard 7498-2).

• Based on these cryptographic tools, various security protocols can be designed for direct use in a network. These include SSL/TLS, SSH, IPsec and AAA. They are used to protect different types of network traffic, and operate at different layer levels of the model shown in figure