Analysis-by-Synthesis Echo Hiding Scheme using Frequency Hopping

This work develops an analysis-by-synthesis echo watermarking scheme using frequency hopping to improve robustness and security. First, the host audio signals are transformed and partitioned into several different frequency bands. Each frequency band is then transformed back to the time-domain components that are separated into multiple fractions. Each audio segment is constructed by combining the fractions selected from all frequency bands based on a secret key from a pseudo-noise sequence. The watermarks are embedded in audio segments. In the meantime, the analysis-by-synthesis approach is adopted to perform attacks on the watermarked signals during the watermark embedding process to suggest the adequate amplitudes of echoes. Owing to fractions being scrambled, the chance of watermarks detected and tampered by the third party can be reduced. Additionally, the problem, that it is difficult to correctly embed echoes in long silent intervals, can be overcome by using frequency hopping. Experimental results reveal that the proposed analysis-by-synthesis echo watermarking scheme using frequency hopping can yield better robustness and security than the conventional echo watermarking schemes.