The Discrete Pascal Transform (DPT) has been proved remarkably useful for edge detection, filter design, discrete-time
signal interpolation and data hiding. In the present work a new blind fragile data hiding technique for secretly embedding
messages into color images, is proposed. The embedding procedure is based on dividing each color image component
into even-sized blocks. Information embedding is determined by monitoring the lower-right corner of the DPT
coefficient matrix. This particular coefficient suffers the highest change for small pixel modifications. The embedding
affects the coefficient's sign. In case that the sign is not the desired one, i.e. negative for a message bit value of '0' and
positive for a message bit value of '1', it is changed by repeatedly adding to the block or subtracting from the block the
identity matrix. This process is based on the DPT properties and on the sensitivity of the lower-right coefficient in even
the smallest pixel changes. The embedding algorithm takes care of the underflows or overflows that may occur during
the consecutive additions or subtractions. The method is evaluated in terms of capacity and image distortion.
Experiments are conducted using different images and block sizes namely 2x2 / 4x4 / 8x8 / 16x16, and the overall
performance of the scheme is quantified. Block size greatly affects capacity and stego-image quality. Comparisons with
existing methods prove the superiority of the proposed method.
Transform domain methods have dominated the watermarking field from its early stages. In these methods some coefficients are selected and modified according to certain rules. The two most important numbers in this process are the length and the position of the watermark. These are usually heuristically chosen. In order to handle this problem, an adaptive scheme for the selection of the proper coefficients is analysed in the present communication.