In constrained networks, multicasting may be preferred over unicasting because of its better energy footprint. The inherent necessity of group management makes securing multicasting specially challenging. This work introduces a characterization of secure group communication and specifies the properties to be achieved. The security properties are derived from ISO/IEC 27000 and adopted to the specialties of multicasting. A validation of state-of-the-art security solutions in constrained networks against the criteria proves the need for future investigations and improvements, especially in the area of sender authentication.