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Abstract

A system for embedding auxiliary digital information (D.sub.i) into an existing primary digitally encoded signal (X.sub.n) to form an unobjectionable composite digital signal (C.sub.n). Auxiliary data bits (D.sub.i) modulate a pseudo-random (e.g., PN) sequence (125) to provide an auxiliary data sequence (160) that is used to modify the Least Perceptually Significant Bits (LPSBs) (180) of successive multi-bit samples (120) of the primary signal. In a cross-term compensation embodiment (300, 400, 1000), a correlation (V) between the PN sequence and the sample bits is determined, and compared to the auxiliary data bits (D.sub.i) to determine whether there is a desired correspondence. The LPSBs in the samples are toggled (360), if necessary, to provide the desired correspondence. The selection of LPSBs to modify accounts for a desired noise level of the auxiliary data (D.sub.i) in the primary signal (X.sub.n). LPSBs may be selected to be modified based on a sparse PN sequence (250) to achieve the desired noise level and to conceal the presence of the auxiliary data (D.sub.i). The data to be hidden can be any digital data, while the primary signal is any uncompressed or compressed digitally sampled process, including, for example, audio or video data.

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