A digital differential steganographic system and method includes a master key that is generated from an unmarked media, a mark-point reservoir created from the unmarked media and containing a set of viable candidate mark points for the unmarked media, and a mark-point applicator to insert data into the unmarked media at selected mark-points chosen from the mark-point reservoir creating a digital watermark. The method includes using an original unmarked media, shaping and testing marks in the original media for predictable distortion, verifying embedded marks at point of insertion in the original media, minimizing mark energy and duration for least-perceptible change, and using non-distributed, unmarked media of the original media as a master key.