**3. Conclusion**

316 Applications of Digital Signal Processing

Fig. 6. An average of the spectrogram of projections of Radon of a fragment of the image

In figure 7 the two-dimensional dependence diagram of a magnitude average calculated on a set of image Radon transforms is shown where peak of normalized averaged spectrum located at 10**º** of Radon transform for angles from [5**º**..15**º**], applied to the image with an initial rotation angle of 10º and image scaling factor varied from 1 to 0,1 by 0,1 step. Even at 0.2 scale coefficient the maximum, which corresponds to correct rotation angle, is visible, so rotation operation can be undone. In figure 6 values of spectrogram average of Radon transform (rotation angles from (0**º**..20**º**)) for 80 images obtained from one camera and

Fig. 7. Dependence of a normalized mean value of averaged spectrum on scaling factor and

dimension 1024x1024 pixel for corners from 0 to 360º

rotated by 10**º** (a) with histograms (b) are shown.

angle of a Radon projection

The methods of digital cameras identification allow defining the fact of origin of digital images from the specific camera. In comparison with artificial digital watermarks embedded by either the special software, or device modification, identification based on innate difference of every single camera allows to identify cameras by the analysis of statistical regularities in digital media. Explicit advantages of the given identification methods are their applicability to images of consumer cameras without necessity of internals access or camera firmware modification. Methods of cameras identification on the basis of processing differences allow to identify cameras vendors. Methods of identification based on nonuniformities of record path allow to identify separate copies of one model of camera. Essential hindrance for correct identification of cameras is scaling and rotation of the images which are exposed to identification process. To ascertain the fact of rotation and its reversing the Radon transform with the subsequent projections processing by Fourier transform can be used.
