# Protecting Data at Risk of Unintentional Electromagnetic Emanation: TEMPEST Profiling
## 3 Sources of Electromagnetic Leakage
### Conductors  
Switches, contacts, relays, power cables, wires, connectors, and other components emit radio frequency or acoustic energy whenever a device processes information electrically. The emanations can be transmitted over considerable distances through free space or be induced into nearby conductors such as signal lines, power cables, telephone lines, or water pipes, and then conducted along these paths for some distance. The information emitted by these devices can lead to sensitive data reconstruction [8]. The authors of [70] investigated the process of reconstructing a personal computer (PC) display image. The power cable, linked to the external electrical grid, acted as an antenna for both emitted and conducted noise, resulting in a significant security concern (Figure 1). Interfering signals generally appear in the form of EM waves emitted into the surrounding space by radiation or conducted currents emitted along various conductors connected to the involved hardware. In most cases, there is an interaction between these signals. Radiated interference is caused by induced currents in conductors connected to or near hardware, such as feeders and transmission lines. Similarly, an unshielded conductor transmitting interference signals can act as a transmitting antenna. Conductors that connect \begin{table}
\begin{tabular}{c c c} \hline \hline
**Manufacturer** & **Scanner** & **Description** \\ \hline \multirow{6}{*}{Eurotempest} & FB5000-A & Based on the Avision FB-5000 A3 scanner. \\  & Fulfills Level A requirements. \\ \cline{2-3}  & GT-1500-B & Based on the Epson GT-1500 scanner. \\  & Fulfills Level A requirements. \\ \cline{2-3}  & 2500-A & Based on HP Scanjet Pro 2500 scanner. \\  & Fulfills Level A requirements. \\ \cline{2-3}  & 3500-A & Based on HP Scanjet Pro 3500 scanner. \\  & Fulfills Level A requirements. \\ \cline{2-3}  & 4500-A & Based on HP Scanjet Pro 4500 scanner. \\  & Fulfills Level A requirements. \\ \cline{2-3}  & HP Flow 7000-A & Based on HP Scanjet Enterprise Flow 7000 scanner. \\  & Fulfills Level A requirements. \\ \hline \multirow{3}{*}{OSPL} & TCS4500-A and -B & Based on HP Scan Jet Pro 4500 fn1. \\  & Fulfills Level A and B requirements. \\ \cline{2-3}  & TCS2500-A and -B & Based on HP Scan Jet Pro 2500 f1. \\  & Fulfills Level A and B requirements. \\ \hline \multirow{2}{*}{Siltec} & TEMPEST Avision & Avision-based A4 scanners. \\  & Fulfills Level A, B, and C requirements. \\ \hline \hline \end{tabular}
\end{table} 
Table 4: _Cont._  
Figure 1: Reconstruction of PC display from common-mode noise emitting on electrical power line (source [70]). multiple devices, whether internal or external, in addition to the basic functions of providing energy transport between two points, act as an interfering medium. The conductor then plays the role of a receiver. Interferences can also be reflected from conductors by EM radiation or conduction. The conductor then becomes the transmitter. A solution that can eliminate interference in conductors is to reduce the sensitivity of the cable to the unacceptable effects of electromagnetic fields. For this purpose, it is recommended to use shielded cables and symmetrical wires in addition to disturbed cables. In [71], the author describes cable products for military, marine, and aerospace applications that are designed to provide superior EMI protection. One of the most known shielded cables are Black Box cables used to connect serial devices (printer, monitor) and are protected from interference by 100% aluminum foil [72]. One of the fully shielded, end-to-end (E2E) cabling systems is Siemon's TERA (Watertown, CT 06795-04000/USA) cables, tested for superior performance and security and validated for TEMPEST high-security applications [73]. The cables are terminated with connectors with a slim, insulated quadrant design that accepts one, two, and four patch cord pairs.