Data embedding for secure communications

We expand on a new technique for embedding digital information into G.711 encoded speech signals for the purpose of secure data communication. Using the method of types as a tool to analyze the statistical nature of a digital speech signal, we demonstrate a scheme that is capable of embedding tip to 1.6 kbits/sec of additional information into a host signal at an average embedded error rate of 10/sup -4/. This additional bandwidth can be used for the purpose of secure communications and has some intrinsic properties that are very attractive for the proposed application. We suggest such a scheme as a possibility for use in existing telecommunications networks. The overall goal of this approach is to increase the data throughput of a given channel without increasing the transmitted data rate or changing the transmission codes, network protocols or source compression methods. In accomplishing this task, we offer the embedded data stream as a transport for an encrypted signal and argue that the resulting mechanism represents a quite natural multilevel approach to secure communication.