ABSTRACT Even though the hierarchical group communication is a most prominent communication method for a various type of applications, featured by some hierarchical communication rules, it has not been effectively investigated in the security aspect. This paper provides a information about private hierarchical group communication and specific confidentiality requirements and efficient key management protocol satisfying these requirements. This work is proposed based on the frame of a national French project which includes the international telecom companies EADS, INRIA, CNRS and ENST-Paris. The project was called SafeCast, which deals with the group communication in PMR networks that are mainly used mainly by security corps like police, fire fighters, soldiers etc in the areas, where it is difficult to have network infrastructures, such as war, battles or a natural disaster like earthquake, tsunami, tornado etc.