Nowadays, collaborative and group-oriented applications are becoming popular. Group communication services such as chat, news, on-line games and simulation services that involve communication over open networks attract many attentions. The security challenge for multicast is in providing an effective method for controlling access to the group and its information. A primary method of limiting access to information is through encryption. So the security of the group is related to the security of its key and key management protocols support the security of it. In fact, a group key management protocol supports protected communication between group’s members. Group key management is one of the basic building blocks in securing group communication. Key management has an important role in access control to group key and as a result in group communication. Using one desirable group key management protocol not only provide group security but also will enable it to adapt itself with events that changes the number of group members. A group key management protocol helps to ensure that only members of a secure group can gain access to group data (by gaining access to group keys). Group key management protocols are divided into three ltr"
