Title :
Capacity of text marking channel
Author :
Low, Steven H. ; Maxemchuk, Nicholas F.
Author_Institution :
Dept. of Comput. Sci., California Inst. of Technol., Pasadena, CA, USA
Abstract :
We have proposed earlier watermarking text documents by slightly shifting certain text lines. Such a text line represents a noisy channel, and marking represents the transmission of a signal through this channel. The power of the signal represents the size of the shift and must be small for the marks to be imperceptible. We formulate the channel capacity under a constraint or individual signal power. We show that to achieve the capacity, the shifts should be normally distributed, have maximum power, and adjacent shifts should be negatively correlated.
Keywords :
Gaussian channels; channel capacity; copy protection; image coding; noise; normal distribution; security of data; centroid detection; centroid measurements; correlated noise; document profile; image watermarking; negatively correlated adjacent shifts; noisy channel; normally distributed shifts; parallel Gaussian channels; signal power constraints; signal transmission; text documents watermarking; text line; text line centroids; text marking channel capacity; Additive white noise; Channel capacity; Character recognition; Copyright protection; Facsimile; Gaussian noise; Printing; Propagation losses; Robustness; Watermarking;
Journal_Title :
Signal Processing Letters, IEEE
