Image Number 19 for United States Patent #7817817.
A method of concealing data in images imperceptibly alters curves therein, such as through adding a value representing the data to be hidden to each of a number of B-spline control points representing the original curve. The altered control points characterize the imperceptibly altered curve, which replaces the original curve in the image. The altered control points may be later extracted from the image and compared with the original control points to determine the hidden value. Prudent selection of the values altering the control points as well as an iterative alignment-minimization algorithm in the detection process provides protection against numerous techniques for preventing the hidden values from being recovered.