a watermarking method converts a watermark message into a frequency shift keying signal and embeds the fsk signal in a host signal . the spectral properties of the fsk watermark signal facilitate its detection , even in applications where the watermarked signal is corrupted . because of these properties , the fsk watermark signal can perform the dual function of identifying the watermark &# 39 ; s presence and orientation in potentially corrupted media , and also conveying a hidden message in the host signal . such a watermark may be referred to as a self - orienting watermark