On Tuesdays the USPTO issues new patents. Both of today's Spotlight Patents concern aspects of digital watermarking. Assigned ot Cryptodyne Systems, Inc., the first patent addresses techniques for implementing digital differential steganographic techniques. Assigned to Xerox, the second patent addresses techniques for watermarking images or image portions, such as saturated text.
8,107,668, "Digital differential watermark and method," assigned to Cryptodyne Systems, Inc.
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.
8,107,099, "Watermarking," assigned to Xerox.
A watermark is provided for use with images or image portions, such as saturated text. The watermark is provided as a modulation to the optical density of a public image or image portion wherein both modulated and unmodulated portions of the public image or image portion have an optical density that is beyond a threshold optical density beyond which the human visual system has a low sensitivity to optical density variations. Alternatively, the modulation is made at such a low amplitude as to be difficult to perceive by the human visual system. The modulation may be applied via an overprinting operation. Alternatively the modulation may be applied to image data prior to printing.