A system and method of retrieving a watermark in a watermarked signal are disclosed. The watermarked signal comprises odd and even overlapped blocks where the watermark is contained in the even blocks. The method comprises, for each k-th even block, subtracting the two adjacent odd numbered blocks from the k-th even block of the watermarked signal to retrieve s*k(n), transforming s*k(n) into the frequency domain to generate Sk(ƒ), calculating a phase of Sk(ƒ) as φ(ƒ) and a phase of Sk(ƒ) as φ(ƒ), calculating the difference Ψ(ƒ) between φ(ƒ) and φ(ƒ), unwrapping Ψ(ƒ) to obtain the phase modulation {tilde over (Φ)}k(ƒ), and using a Viterbi search to retrieve the watermark embedded in {tilde over (Φ)}k(ƒ).