Selective encryption and scalable speech coding for voice communications over multi-hop wireless links

With the rapid deployment of wireless LAN and the future development of mobile ad hoc networks, multi-hop wireless communications links are expected to become much more common. How to achieve reliable and efficient, yet secure, voice communication over such multi-hop wireless links is an important issue. This paper proposes and investigates a combination of scalable speech coding and selective encryption for secure voice communication over multi-hop wireless links that addresses both the efficient use of network and node resources and security against unwanted eavesdroppers. It is shown that when the Shannon lower bound is satisfied with equality for rate distortion optimal scalable coding, transmission of the enhancement layer in-the-clear provides no information regarding the core layer. A specific example of combining selective encryption with MPEG-4 scalable speech coding demonstrates the effectiveness and efficiency of the approach.