## 5 Conclusions  
This article presents the results of research and analysis of the possibilities of using secure fonts (secure symmetrical and secure asymmetrical) in the protection of processed text data against electromagnetic infiltration. The analyses were based on the visual method as the main method in the classification process of revealing emissions. The presented secure fonts are a new and evolving method that can support the protection of text data against electromagnetic eavesdropping. Any new solution that can decide on information security must be subject to verification. The best approach in this case is to assess the effectiveness of the method by independent institutions, which also have various measuring devices. Thus, it is possible to carry out independent analyses, and their results can fully confirm or contradict the suitability of the methods in the area of application under consideration. The fonts presented in this paper can be applied as a security measure against electromagnetic compromising emissions, by applying the security policies that have to be applied to the computer and communication systems. The tests of secure fonts were carried out at two independent institutions: Military Communications Institute (Poland) and Special Telecommunications Services (Romania). These institutions used various receiving systems (Military Communications Institute: Tempest Test System DSI 1550A; Special Telecommunications Services: Rohde&Schwarz FSET22 and Rohde&Schwarz FSWT), which additionally confirmed the effectiveness of the new proposed method. The tests were carried out in anechoic chambers. The source of unwanted emissions was a typical stationary computer set (in case of MCI) and a portable computer (in case of STS). In each case, revealing emissions were detected, which were registered and rasterized. The images obtained in this way showed the superiority of the secure fonts over traditional ones in the field of protection of text information against electromagnetic penetration. This applies to cases when the font character size was not larger than 24 points. Character recognition is possible for larger sizes. For traditional fonts, the text was readable for virtually any size of characters. The conclusions are also true for analogue graphic standard. In Figure 23, each considered font is presented. The size of characters was equal to 14 points and the text written by using secure fonts is very difficult to read. The presented method of using secure fonts in the protection of text data against electromagnetic infiltration will still be developed in the future. The fonts must be fully usable, i.e., contain the required characters for the full editing of text documents. The main originality of the paper stands in the use of the secure symmetrical and secure asymmetrical sets of characters and numbers that were patented by the Polish Office Pattern in the form of the Industrial Design (No. 24487) and Patent (No. 231691). We propose the use of these fonts  
Figure 23: Image reconstructed based on sensitive emissions measurement on frequency 640 MHz (\(BW\) = 50 MHz, the size of characters-14 points), from the top: secure symmetrical font, Arial font, secure asymmetrical font, Times New Roman font (VGA standard). to be introduced as one of the official TEMPEST countermeasures in the classified NATO documents, that impose the regulations of the activities involved in this technical field and which represent national security measures for the IT equipment of each Member State (NATO and EU).Their security have been tested by the MCI, Poland, in their laboratory, but here it is the first time when they are also checked in STS, Romania, in an independent laboratory with a different setup and test equipment. Since in the two testing environments there have been obtained similar results, that asses the fact that the secure symmetrical and secure asymmetrical sets of characters and numbers are less vulnerable to interception through revealing electromagnetic emissions.