Abstract: A secure audio teleconferencing system is disclosed. The secure teleconferencing system comprises a centralized facility or bridge to which a plurality of participants is connected. The role of the bridge is to receive encrypted message signals from the participants and to add the encrypted message signals, modulo some known number. The result is then transmitted to the participants. Each participant is able to decrypt the modular sum of encrypted message signals, to obtain the desired ordinary sum of clear text message signals. In accordance with the invention, the message signals remain encrypted throughtout processing by the bridge. There are no non-encrypted messages.

Abstract: Circuitry generates a plurality of differently-phased m-sequences (or pseudo-random sequences) for scrambling/descrambling of all tributary data signals at a multiplexer/demultiplexer. By scrambling/descrambling at the tributary levels and thus at the lower tributary clock rates, less complex circuitry can be employed, and by properly selecting the tributary scrambling sequences in accordance with the teachings of this invention, a desired high speed line sequence can be attained.