# Protecting Data at Risk of Unintentional Electromagnetic Emanation: TEMPEST Profiling
## 2 Related Work
Authentication can also be used to confirm the identity and credibility of users. If side-channel attacks cannot be prevented or detected, they can be mitigated by reducing their impact or effectiveness. This can involve implementing different strategies, including encryption, key management, or appropriate countermeasures [20]. In [2], the author investigated compromised emanation from CRTs, laptops, and flat panel displays. He successfully reconstructed an image on a CRT display from a three-meter distance. The authors of [21] published another study on information leakage in optical emissions. They demonstrated that LED status indicators on data transmission devices can transmit modulated optical signals correlating with the information being processed. According to [22], eavesdropping on emitted video signals is another EM security issue because the information shown on displays requires a high level of security, and the amount of related data is much greater than others. The emanation strength of wireless devices is weaker than the displayed signal, making it difficult to decipher the original signal. Wireless communication is regulated worldwide. The choice of frequency range and RF communication system power can be determined by specific application requirements and existing regulations [23]. The industrial, scientific, and medical (ISM) bands range from 2.4 GHz to 2.5 GHz and are determined by the International Telecommunication Union (ITU) radio regulations (RR). The family of standards created by the Institute of Electrical and Electronics Engineers (IEEE) 802.11 specifies the set of medium access control (MAC) and physical layer protocols for implementing computer communication over wireless local area networks (WLANs) [24]. The standards use 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz frequency bands. Since wireless keyboards use the ISM band, information can also be intercepted via wireless local area networks [25]. It should be noted that well-designed systems take into account various factors such as data transfer rate, quality of service, interference, security, and coverage. The security risks caused by wireless signal interception, regardless of the communication protocol, radio noise, or physical obstacles, are discussed in [4]. In [1], the authors describe the problems caused by EM emissions from keyboards and communication data. They were able to decode the keys pressed on the keyboard by the operator. The authors of [26; 27; 28] discussed the security risks of wireless USB keys because an unencrypted input signal can be intercepted and used to access the attached device. One of the issues related to EM leakage is conducted emission. A conductor charged to a nonzero potential or carrying electrical current acts as an antenna that releases energy into the environment in the form of an EM wave. Emissions can be conducted directly into the circuit on the input lines or through near-field energy that is capacitive coupled (electrical field). Conductive coupling occurs when the coupling path between a source and receptor forms contact through a wire, cable, or transmission line [29]. Conductive emissions can also be conducted unintentionally through near-field energy magnetically coupled to a circuit (a magnetic field). Energy from these fields can couple to other conductors within the device and radiate into the environment outside the device. Conversely, every conductor acts as an antenna that converts the energy of the EM field into voltages and currents [30]. The possibility of EMI caused by unintentional emissions from cables is discussed in [31]. The authors studied the emission of unshielded twisted pair (UTP) cables carrying high-frequency signals (up to 10 GHz) and found that UTP cables emit unwanted emissions in the 6 GHz band. A printed image can be reconstructed by receiving radiation emitted by a laser printer [1]. The authors of [32] improved the measurement of monochrome laser printer radiation using several special test patterns.