A hardened VoIP system is presented that includes secure push-to-talk voice functionality. Through the addition of encryption, authentication, user filtering, and integration with new and existing LMR systems, a secure voice platform ensures malicious software, unauthorized access, and brute force security attacks will not compromise the voice communications of the system. The VoIP system is engineered to ensure graceful system degradation in the event of maintenance activities, natural disasters, and failure modes. The hardened VoIP system offers the functions of a LMR trunking system while utilizing broadband connections. Private calls, group calls, Emergency Alarms with covert monitoring capability, scanning, and priority scanning may be incorporated into the system. The system includes a VoIP controller that serves as a trunking controller, manages available VoIP based conference bridges, and assigns them as needed to the parties involved in each voice call.