Direct sequence voice scrambling scheme#x2010;a new technique for secure communications

摘要

Communication security is getting more and more important. Although the encryption of digitized speech is very attractive, direct scrambling of the analog speech waveforms continues to be an important approach due to a strong desire for the use of existing telephone networks with standard telephone bandwidth at acceptable speech quality and cost. In this paper, a new approach for analog speech scrambling, a Direct Sequence Voice Scrambling (DSVS) scheme, is proposed, in which the spread spectrum concept is borrowed but combined with a newly developed bandwidth reduction technique. The system design, performance analysis, practical considerations and simulation results are presented in detail in this paper. The analysis indicates that the DSVS scheme can provide the following advantages: small residual intelligibility, high degree of security, small bandwidth expansion, no time delay and only slight degradation of speech quality.