Steganography integrated into linear predictive coding for low bit-rate speech codec

Abstract

The extensive use of Voice over IP (VoIP) applications makes low bit-rate speech stream a very suitable steganographic cover media. To incorporate steganography into low bit-rate speech codec, we propose a novel approach to embed information during linear predictive coding (LPC) process based on Matrix Embedding (ME). In the proposed method, a mapping table is constructed based on the criterion of minimum distance of Linear-Predictive-Coefficient-Vectors, and embedding position and template are selected according to a private key so as to choose the cover frames. The original speech data of the chosen frames are partially encoded to get the codewords for embedding and then the codewords that need to be modified for embedding are selected according to the secret bits and ME algorithm. The selected codeword will be changed into its best replacement codeword according to the mapping table. When embedding k (k > 1) bits into 2kź1 codewords, the embedding efficiency of our method is k times as that of LPC-based Quantization Index Modulation method. The performance of the proposed approach is evaluated in two aspects: distortion in speech quality introduced by embedding and security under steganalysis. The experimental results demonstrate that the proposed approach leads to a better performance with less speech distortion and better security.