With emerging of new cooperative applications, the group communication is clearly become a very important concept within the network architecture. The multicast transmission is appeared as the most efficient way to send some data to a specific group composed of several participants like used in multimedia applications (audio and video conferences, video diffusion,...) But today, we can see that commercial multicast deployment is not a reality yet. This model presents some limits such as: scalable routing problems, address allocation problems and mainly security issues because any host can send data to IP multicast address and any host can join Nowadays the increasing interest in network communication through the using of the Internet requires some services such as authentication, integrity and confidentiality to transport securely data. The lack of security in multicast communications is essentially due to the difficulty to develop solutions which are efficient and fault tolerant. In our tutorial, we present : * Security issues within group communications and why the approaches to secure the unicast communications cannot be directly applied to group communications. * Research work related to key management and key distribution. * Research work related to source authentication. * Fault tolerance within group communications.