Symmetric Encryption Algorithm in Speech Coding for Defence Communications

In battlefield, messages must be encrypted to provide protection from enemy interception. Several speech coding algorithms have been developed to provide secure communications. FS1015 LPC in 1984, FS1016 CELP in 1991and FS MELP in 1997 became official federal standards. In 2002, the US DoD adopted enhanced MELP (MELPe). Later on in 2007, US Naval Research Laboratories have designed Variable Data Rate (VDR) voice processor. Although certain degree of inherent security is ensured in all the above coding algorithms by way of compression techniques, strength of security in these algorithms is weak as the codecs using the above algorithms are vulnerable to interception. Explicit encryption gadgets need to be provided as accessory to provide strong secure communications. In this paper, we have described an algorithm which provides robust and secure communications. This Robust Secure Coder (RSC) is backward compatible with the existing codec’s and operates at marginally higher bit rates when switched to secure mode.