Multilevel Secure Teleconferencing over Public Switched Telephone Network

Two-way group voice communications, otherwise known as teleconferencing are common in commercial and defense networks. One of the main features of military teleconferences is the need to provide means to enforce the Multilevel Security (MLS) model. In this paper we propose an architecture and protocols facilitating MLS conferences over Public Switched Telephone Network (PSTN). We develop protocols to establish secure telephone conferencing at a specific security level, add and drop conference participants, change the security level of an ongoing conference, and tear down a conference. These protocols enforce MLS requirements and prevent against eavesdropping. Our solution is based on encryption methods used for user and telephone authentication and message encryption, and trusted authentication centers and certificate authorities. We provide an initial estimate of signaling delays of our protocols incurred due to the enforcement of the MLS requirements.