Electromagnetic Eavesdropping

Abstract

Protection of information against electromagnetic penetration is a huge challenge. Especially this issue applies to computer station that processes protected information and that is a source of electromagnetic disturbances. These disturbances could be correlated with processed graphic information. Therefore, very often, they are called valuable or unintentional emissions. To protect the information, different methods of engineering of electromagnetic compatibility are used, e.g. electromagnetic gaskets, signal and power filters and electromagnetic shielding. The use of these methods causes a special device to become very heavy, and the looks of such device aren’t nice. A new universal solution based on safe fonts is proposed. Safe fonts protect processed information against electromagnetic penetration in each case of graphic source of valuable emissions. These fonts protect not only Video Graphics Array (VGA) but also Digital Video Interface (DVI) standards. These fonts are also useful from electromagnetic protection’s point of view in the case of the use of laser printers. All analyses are based on images reconstructed from valuable emissions. These emissions are measured in a range of frequencies from 100 MHz to 1.5 GHz. Safe fonts are simple solution that counteract electromagnetic eavesdropping process. They can replace expensive solutions based on shielding, zoning and filtering.