Formant enhancement based speech watermarking for tampering detection

Unauthorized tampering in speech signals has brought serious problems when verifying the originality and integrity of speech signals. Digital watermarking can effectively check if the original signals have been tampered by embedding digital data into them. This paper proposes a tampering detection scheme for speech signals based on formant enhancement-based watermarking. Watermarks are embedded as slight enhancement of formant by symmetrically controlling a pair of linear spectral frequencies (LSFs) of corresponding formant. We evaluated the proposed scheme with objective evaluations concerning three criteria that are required for tampering detection scheme: (i) inaudibility to human auditory system, (ii) robustness against meaningful processing, and (iii) fragility against tampering. The evaluation results showed that the proposed scheme could provide satisfactory performance in all the criteria and had the ability to detect tampering in speech signals.