Assessing the Security of TEMPEST Fonts against Electromagnetic Eavesdropping by Using Different Specialized Receivers

Abstract

The main topic of the present paper is the printed text protection against electromagnetic infiltration. There are many solutions to protect such data. One of these methods is the one that uses computer fonts that are characterized by special shapes. The suitability of the solution has to be confirmed by many tests and analyses. An important element of such researches is the class of receiving devices used. In the case of measurements of the valuable emissions arising from electronic data processing of the printed text, typical receivers that are used for measurements of electromagnetic compatibility cannot be used. They have to be dedicated devices for measuring the very low level of signal that arises unintentionally. The sensitivity of the receiver must be very high in wide measuring bands. In addition, in order to assess the method of preventing electromagnetic infiltration, it is important to verify it by independent institutions. An additional advantage is the use of different receivers in the assessment process. This paper presents the results of studies made regarding the suitability of two sets of fonts with special shapes (secure symmetrical and secure asymmetrical) in secure information processing. The analysis of the fonts was based on visual examination, a basic method of preliminary assessment of electromagnetic emissions correlated with processed text information, of the images reproduced from unwanted emissions. The tests were carried out at two independent institutions, Military Communication Institute—Poland, Special Telecommunications Services—Romania, using three different types of receivers: Tempest Test System DSI-1550A, Rohde & Schwarz FSET22 and Rohde & Schwarz FSWT. The images obtained in the two independent laboratories with different setup and test equipment confirmed thus without doubt the possibility of using special fonts as the solution against an effectiveness of electromagnetic infiltration. The above assessment is correct, regardless of the used receiver and the environment of implementation of the secure fonts.

Method of Colors and Secure Fonts Used for Source Shaping of Valuable Emissions from Projector in Electromagnetic Eavesdropping Process

“…As for other devices used for graphical display of processed information, it is advisable to propose solutions that can counteract the generation of emissions that can be correlated with the original signal. In the further part of the article, the authors analyze the effectiveness of the safe fonts [6,31], that proved to be efficient for the protection of processed text data for computer monitors and laser printers. Then the safe fonts were indicated as a universal solution that can be used in various devices processing text data to protect them against electromagnetic penetration.…”

“…The aim of this article is to present the existing risk related to the use of typical projectors in a system with special devices that are dealing with confidential data and to propose solutions to reduce the level of this risk. The possibility of using special computer fonts was proposed and their effectiveness was compared with traditional fonts [15,30,31]. Due to the specificities of the modern presentations, this solution was connected with the method of colors, based on the appropriate selection of the background color and the color of the text characters.…”

“…The safe fonts were introduced in Patent (No. P.408372) and analyzed in [6,31], but only with black fonts on white background, never in combination with the method of colors. While safe fonts directly counteract the formation of valuable revealing emissions (drawings), the method of colors can have two applications.…”

Analysis of Compromising Video Disturbances through Power Line

“…24487 (2018) and patent no. 231691 (2019), has also been analysed in [ 18 ]. The effectiveness of the security provided by these fonts in the case of the use of display colours was also studied in [ 16 , 19 , 20 ].…”

The Possibility to Recreate the Shapes of Objects on the Basis of Printer Vibration in the Additive Printing Process

“…It has been assumed that if such a measurement system shows the usefulness of these vibrations for the infiltration process during printing, they can also be detected from greater distances. In such a case, vibration signals, similarly to electromagnetic emissions, e.g., from computer monitors [4], can be used for non-invasive acquisition of information.…”