Paper
Two-Dimensional Correlation as a Search Method of Relationship between Pattern Image and Compromising Emanation
- Authors:
- Ireneusz Kubiak
- Abstract
- In the era of technological advance in development of electronic equipment and its widespread application for everyday use, the issues related to protection of information against electromagnetic penetration become the matters of key importance. Each piece of equipment that is used for processing confidential information may happen to be a source of undesired emissions. However, due to design solutions applied to engineering of such devices, the levels of compromising emission signals are very low. To evaluate vulnerability of such equipment to eavesdropping, it is necessary to apply methods that enable picking up substantial information that is hidden in noise. In particular, it refers to signals that are correlated with signals of graphic transmission tracks of computers since capturing such signals enables reproduction of images that are displayed on the screen of the “eavesdropped” computer. Use of the methods that are suitable for digital processing of images, even modified for needs of successful electromagnetic infiltration, is insufficient to achieve the desirable results. Hence, it is necessary to seek for other more powerful and efficient methods, where the method of two-dimensional correlation between the pattern image and fragments of the images subjected to the analysis seems to be the most promising one, where the images can be reproduced from the compromising emanation with use of the half-tone screening method. For such cases, the correlation factor never reaches the levels that correspond to a strong or even a weak correlation since its values for those fragments of the images under the analysis that comprise signs consistent with signs of the pattern reach the values of about 0.07. Therefore, one has to adopt a certain criterion that makes it possible to classify recognized fragments of images. The paper outlines the opportunities offered by application of the Zeroing Filter. The approach bases on the analysis of the amplitude value for the pixel that indicates potential position of the pattern image in the image under analysis and comparison of that amplitude against the average amplitude of adjacent pixels. When the differential amplitude exceeds the predefined threshold D the methods assumes that the location within the analyzed image with the desired sign of the pattern image is detected. The studies with the aim to confirm legitimacy of the assumed method were carried out for real images that had been acquired form signals of compromising emanation recorded for the special unit under test.
- Keywords
- Electromagnetic Infiltration; Protection of Information; Compromising Emanation
- StartPage
- 81
- EndPage
- 95
- Doi