Secure audio teleconference

Abstract

A number of alternative encryption techniques have been suggested for secure audio teleconferencing implementable on public switched network, in which the centralized facility, called bridge, does not hold any secret. The role of the bridge is to synchronously add simultaneous encrypted signals, modulo some known number, and then transmit the result to all the participants. Each terminal has a secret key, with which it can decrypt the above modular sum of encrypted signals to obtain the desired ordinary sum of cleartext signals. Secrecy of the systems is analyzed. Some of which are provably secure, assuming the existence of one way functions, and for the others we have partial cryptanalysis. We also present a N-party identification and signature systems, based on Fiat and Shamir’s single party systems, and another N-party signature system based on discrete-log problem. Our system have communication complexity 2N times that of the basic Fiat-Shamir systems (as compared to a factor of N 2 in the direct application of the basic scheme to all pairs).