关键词: 语音隐写, 动态搜索, 分数基音延迟, 自适应多速率语音编码, 隐写安全性

Abstract:

In this paper, we present a speech steganography algorithm based on dynamic search of fractional pitch delay. The algorithm can divide the candidate value set of fractional pitch delay into 2 ^x subsets according to the needs of the covert capacity (x bits/subframe), where each subset represents different x bits of information. In the closed-loop pitch search process, the algorithm can select for each subframe the best candidate value of pitch delay that can not only denote the secret information but also make the interpolated normalized correlation coefficient largest. In this way, the impact of steganographic operations on the original carriers can be effectively reduced. Taking adaptive multi-rate speech codec widely used in the current Voice-over-IP systems as an example, the performance of presented algorithm has been evaluated from the aspects of covert capacity, imperceptibility and anti-detection, and compared with related works. Experimental results show that the proposed steganographic algorithm can achieve better steganography security (better resistance to detection and imperceptibility) than the existing steganographic methods based on pitch delay, while maintaining relatively high steganographic capacity.

Key words: speech steganography, dynamic search, fractional pitch delay, adaptive multi-rate speech codec, steganographic security