###### Abstract  
An important issue in the protection of information against electromagnetic penetration is the possibility of its non-invasive acquisition. In many cases, getting hold of protected information involves recreating and presenting it in a readable and understandable form. In particular, this applies to data processed in graphic form and in such a form presented on the side of eavesdropping system. The effectiveness of reconstructing data in graphic form requires knowledge of raster parameters, i.e., the line length and the number of lines of the reproduced image. This article presents new measures allowing for the determination of the correct number of lines in an image. The maximum value of the measures has been proposed as a criterion for the correctness of determining the number of image lines. A predetermined number of image lines was assumed as the input data, which was determined on the basis of the analysis of the amplitude variability of the recorded revealing emission signal. The result of the considerations of the effectiveness of the measures adopted in the process of electromagnetic infiltration was the indication of methods that allow for the correct determination of the number of lines of the reproduced image. The correct number of image lines allows the use of the coherent summation algorithm of tens of images. s _applied_  
_sciences_  
**Citation:** [PERSON]; [PERSON] [PERSON]. Devices intended for the processing of classified information require prior research in the scope of the assessment of measured electromagnetic emissions in laboratory conditions, i.e., in electromagnetically tight anechoic chambers(Figure 2). Meeting the requirements of information protection by the tested device inside the anechoic chamber guarantees information security in any other electromagnetic environment, in the environment surrounding us in particular. The assessment is related to the determination of the degree of correlation of these emissions with the information processed [21; 22; 23]. This applies to devices that process data in graphic form in particular. The importance of this type of source of undesirable emissions results from the fact that the reconstructed data can be presented in the form of images containing human-readable and -understandable data [24; 25; 26; 27]. In order for the reproduced data to be visualized in the form of images, it is necessary to know two basic image parameters: width (d image line length) and height (number \(B_{Corr}\), of image lines) [28; 29; 30; 31]. These parameters determine the correctness of the reconstruction of the image ready for effective further processing with the use of, e.g., the coherent summation algorithm of tens of realizations of the same image, which is possible thanks to a sufficiently long recorded implementation of the signal \(s(t)\) of the revealing emission. It should be noted that in this case the emission source, which is the signal \(x(t)\), must be a periodic signal in which the information about the processed data is repeated cyclically [30; 31]. Such signals are, for example, video signals that excite graphic displays. Incorrect values of these parameters cause the quality of the reproduced image, after applying the image summation  
Figure 1: Surrounding us potential sources of undesirable emissions correlated with the information processed. process, to deteriorate and the data contained in it to become more unreadable (identifiable data becomes blurred, and not sharpened) or to result in an incomplete image (Figure 3). Determining the correct number \(B_{Cerr}\) of the reproduced image line results directly from its ignorance, which is related to a lack of access to the eavesdropped graphic imaging device in the electromagnetic infiltration process. This applies to typical computer monitors as well as any devices equipped with graphic displays, e.g., multifunctional devices. A rough estimate of the raster parameter of the number of lines in an image can be made based on a visual analysis of the reproduced image.