# Protecting Data at Risk of Unintentional Electromagnetic Emanation: TEMPEST Profiling
## 5 Discussion
A Faraday cage scatters the charge or radiation to the outside of the cage and cancels out the charge or radiation inside the cage. The use of a shielded chamber also ensures an EMI-free environment. The chamber filters out unwanted \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Device Type** & **Source** & **Protection Measures** & **Protection Level** & **Manufacturer** \\ \hline \multirow{4}{*}{Computer monitors} & Refresh rate; horizontal frequency; pixel frequency. & Housing; Faraday cage; shielding. & A, B & Eurotempest \\  & & Turning off SSID; & A, B, C & Siltec \\  & RF emission. & Housing; & A, B & Eurotempest \\  & & Housing; & Faraday cage; & A & Cisseure \\  & & Pixel frequency. & shielding. & B & SIPAL \\  & & & A, B, C & C2 \\ \hline \multirow{4}{*}{Wireless keyboards and mice} & \multirow{4}{*}{RF emission.} & Turning off SSID; & & \\  & & changing default SSID & - & - \\  & & name; & data encryption. & & \\ \hline \multirow{4}{*}{Printers} & \multirow{4}{*}{EM radiation.} & TEMPEST filtered AC & A, B, C & Siltec \\  & & TEMPEST filtered AC & Encryption & Eurotempest \\  & & input; & A, B & OSPL \\  & & encryption; & A, B, C & C2 \\  & & shielded cables. & A, B, C & Siltec \\ \hline \multirow{4}{*}{Scanners} & \multirow{4}{*}{EM radiation.} & TEMPEST filtered AC & A, B, C & Siltec \\  & & input; & A, B & Eurotempest \\  & & shielded cable. & A, B & OSPL \\  & & & A, B, C & C2 \\ \hline \multirow{4}{*}{Conductors} & RF; acoustic energy; induced currents. & Shielding cables; symmetrical wires. & Tested for TEMPEST & \multirow{2}{*}{Siemon [PERSON]} \\  & EM interference; inductive coupling. & Increasing distance; EM shielding. & & \\ \hline \multirow{4}{*}{RFID} & \multirow{4}{*}{EM radiation.} & Limiting EM emission of the system. & & \\  & & Increasing RFID chip & & \\  & & complexity; & & \\ \cline{1-1}  & & robust cryptographic computation techniques. & & \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Comparison of devices and TEMPEST protection measurements. background signals and noise, and the internal components are protected from external EM radiation by a special enclosure, ensuring a controlled environment. Manufacturers of active TEMPEST equipment (monitors, scanners, and printers) use existing devices from renowned manufacturers and install appropriate TEMPEST protection measures them (A, B, and C levels). Users without sufficient financial resources can choose equipment with a lower level of TEMPEST protection, but they can complement it with physical protection measures and obtain a satisfactory level of EM protection for security-sensitive data. It is difficult to implement shielding measures for equipment (keyboards, mice, cables, PES, and RFID) that is not directly connected to AC (excluding cables) because their basic functions would be disabled. Solutions for TEMPEST protection are increasing distance, EM shielding of equipment, increasing complexity, include applying robust cryptographic techniques. In addition to direct TEMPEST protection measures on equipment (AC input filtering, EM shields, and cryptography), indirect measures such as RED/BLACK separation and filtering, zoning, masking, and overlaying are also applied. NATO introduces SDIP standards for shielding and zoning. Zoning regulations provide more cost-effective alternatives for the private sector to avoid costly certification. Such alternatives can be used in an environment with a lower level of security, while other TEMPEST measures must be used for security-sensitive data. RED/BLACK separation and filtering imply the physical separation of cables, data flows, and public and private networks to reduce unintentional data leakage. Recent research by air-gapped networks shows that this kind of protection cannot be considered reliable because attackers can use the emanations of individual computer components. Masking and overlaying are techniques that can prevent an attacker from detecting and interpreting emanations. It is very important with these techniques to carefully select the EM noise generator.