Perception-based selective encryption of G.729 speech

Mobile multimedia applications, the focus of many forth-coming wireless services, increasingly demand low-power techniques implementing content protection and customer privacy. In this paper a low-complexity, perception-based partial encryption scheme for telephone-bandwidth speech is presented. Speech compressed by a widely-used speech coding algorithm, ITU-T G.729 CS-ACELP at 8 kb/s, is partitioned in two classes, one, the most perceptually relevant, to be encrypted, the other, to be left unprotected. Encryption of about 45% of the bitstream achieves content protection equivalent to full encryption of the bitstream, as verified by both objective measures and formal listening tests. Low-power, portable devices can, therefore, implement very high levels of speech-content protection at a fraction of the computational load of current techniques, freeing resources for other tasks and enabling longer battery life.