Design and deployment of an integrated data ciphering unit inside a low bit rate voice transcoder for secure voice communications over telephone networks

It is noted that to provide encryption-based secure communication in telephone networks, one of the basic questions to be faced by telephone companies is where to locate the encryption/decryption devices and also how to interface them with their existing telephone switching and multiplexing equipment so that the cost of providing secure communication service to their customers is affordable. To answer this question, an integrated data ciphering unit (DCU) is presented. In particular, the deployment of a DCU inside low bit rate voice (LBRV) transcoder telephone equipment is discussed. The accuracy of an adaptive differential pulse-code modulation prediction algorithm and the impact of errors due to decoding are analyzed, and a specific scheme for the deployment of the DCU inside an LBRV transcoder is proposed to provide a better level of security for voice communication over telephone networks. Some implementation details and a cost analysis are presented indicating that the percentage incremental cost of providing secure communication service to the customers is quite negligible