Novel Method of Hiding Information in IP Telephony Using Pitch Approximation

In this paper a novel steganographic method, called Hide F0, dedicated to IP telephony is proposed. It is based on the approximation of the parameter that describes the F0 frequency (the pitch) of the speaker´s voice. We show that thanks to approximating some fragments of the "fine pitch" parameter in the Speex codec we can create efficient hidden transmission channels. We determined that for Speex working in mode 5 the Hide F0 method can provide a hidden channel with a capacity of ca. 220 bps at the optimal operating point. We also demonstrated that the proposed method offers a significantly more advantageous trade-off between the steganographic bandwidth and steganographic cost than the classic least significant bit (LSB) approach.