Blind Tamper Detection in Audio using Chirp based Robust Watermarking

In this paper, we propose the use of ‘chirp coding’ for embedding a watermark in audio data without generating any perceptual degradation of audio quality. A binary sequence (the watermark) is derived using energy based features from the audio signal and chirp coding used to embed the watermark in audio data. The chirp coding technique is such that the same watermark can be derived from the original audio signal as well as recovered from the watermarked signal. This not only enables the ‘blind’ recovery of the watermark, but also provides a solution for deriving two independent extraction processes for the watermark from which it is possible to ensure the authenticity of audio data and any mismatch indicating that the data may have been tampered with. To evaluate the robustness of the proposed scheme, different attacks such as compression, filtering, sampling rate alteration, for example, have been simulated. The results obtained reflect the high robustness of the watermark method used and is effectiveness in detecting any data tampering that may have occurred. For perceptual transparency of the watermark, Perceptual Assessment of Audio Quality (PEAQ ITU-R BS.1387) on Speech Quality Assessment Material (SQAM) has been undertaken and an average of -0.5085 Objective Difference Grade achieved. Key-words— Chirp Coding, Robust Audio Watermarking, Self-Authentication, Tamper Detection, Wavelet Transform.