A secure audio teleconference system

The authors describe a secure teleconferencing system which can be operated in the public communications network. In this system, advantage is taken of the fact that clear speech must be available at each telephone set for the local participant, and this can be used with a distributed conference circuit to provide a multiparty conferencing system. The network conference control unit knows the addresses of all the participants but its role is limited to provided channel connections and demultiplexing and distributing unaltered signals from the participants. The conference unit does not need to know any security information. The system can operate with a number of security methods, and the users are free to select the techniques that they are most comfortable with. The system is suitable for implementation in digital networks such as the integrated service digital network, and can provide extremely high quality and robust operation.<>