Capacity of text marking channel

We have proposed earlier watermarking text documents by slightly shifting c ertain 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 mark s to be imperceptible. In this paper, we formulate the channel capacity und er a constraint or individual signal power. We show that to achieve the cap acity, the shifts should be normally distributed, have maximum power, and a djacent shifts should be negatively correlated.