This paper presents a new approach regarding the unintended radiation generated by the PS/2 commercial keyboards. It was possible to restore the keystrokes in a controlled environment by receiving the PS/2 bus clock as opposed to receiving the data bus transitions as it has been presented so far in the literature. Examples of keystrokes corresponding to several alphanumeric keys as well as functional keys that are confirmed by galvanic probing of the PS/2 line with an oscilloscope will be presented. The paper presents time domain measurements of the unintended radiation for different keystrokes and also examples of remote reception. We can conclude that the keystroke's compromising radiation can take multiple forms from which the key pressed can be identified with certainty, showing thus a new vulnerability.
KEYWORDS: Signal processing, Computer security, Signal to noise ratio, Computing systems, Signal attenuation, Raster graphics, Telecommunications, Digital filtering, Interference (communication)
The purpose of this paper is to improve the security level of commercial computer systems by analyzing security risks related to compromising emissions and finding the optimal measures of protection. The security threat related to interceptor’s capabilities is a major issue in the process of evaluating the signal to noise ratio at the boundary of protected area. The objective consists in reduction of the probability of detecting compromising emissions which may be eavesdropped at some distance from the computer system using signal processing techniques.
This paper presents a new approach to the TEMPEST compromising signals emitted by the printing devices. From the TEMPEST point of view, only the laser printer diodes and the printer-computer communication signals have been considered as compromising signal generators so far. In this paper we will present some examples of video signal recovery from the compromising signal generated by the laser printer LCD display as well as a number of measurement results of the video signal parameters for particular video display signals which have been selected for this reason.
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