Chapter 3 - The ABS Speech Information Hiding Algorithm Based on Filter Similarity

Abstract

The requirements for adopting information hiding techniques in secret communication are high hiding capacity, real time, and high robustness. For the purpose of real-time speech secure communication, information hiding and extraction algorithms based on ABS speech coding schemes are presented in this chapter. This hiding algorithm substitutes secret speech data bits for Linear Predictive Coefficients (LPCs) in Linear Predictive Coding (LPC). Statistics show that the change of a voiced signal track is very slow and the codebook for LPC vectors is very large in the ABS coding scheme. Therefore a new concept, filter similarity, is proposed to determine the LPC parameters by replacing them with secret speech information, and to generate a multicodebook for saving storage space for secret speech information. Then, the proposed algorithms of the LPC parameter substitution for secret speech information hiding based on filter similarity (LPC-IH-FS) and secret speech information extraction with blind detection-based minimum mean square error (BD-IE-MES) are introduced in detail. To achieve the best effects of information hiding, a dynamic threshold is set up to make an optimal trade-off among hiding capacity, security, robustness, transparency, and real time. Experiments show that the proposed approach meets the requirements of information hiding and secret communication speech quality. Test results indicate that this approach reaches high hiding capacity with excellent speech quality, while complicating speakers’ recognition.