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In this paper, an information recovery process using a horizontal and vertical synchronization frequency detection algorithm, a multiple frame average technique, as well as an image skew correction process is presented. The validity and effectiveness of the proposed procedure are demonstrated using liquid crystal display monitors and a log-periodic dipole array antenna with software-defined radio equipment. In addition, it is shown that real-time video information recovery is possible from a distance of 10 m behind a concrete wall.

Key information of universal serial bus (USB) keyboards at keystroke can be found by analyzing the electromagnetic emanations from the USB cable. The problem with information security such as eavesdropping arises from these emanations. This paper presents the emission phenomenon according to the signal transmission mechanism of USB keyboards and method of measurement and analysis of the leaked signal. Electromagnetic emanations were measured by the antenna and receiver and analyzed by the several signal processing algorithms.

This study verifies the feasibility of information leakage from video cable of digital video display interface. The compromising electromagnetic emanations are estimated by analyzing digital visual interface (DVI) used as video display interface in this research. Leaked signal from DVI cable was measured by near-field probe and digital oscilloscope. Target display is composed with ‘10’ and ‘55’ color as maximum contrast of electromagnetic emanations. Strong frequency band of received signal is near 324 MHz which is related to pixel frequency of target display. Emanated signal filtered with 10 MHz bandwidth at center frequency of 324 MHz is recovered to display. Information leakage from DVI cable at close range is demonstrated by recognizable recovered display.

This study confirms the possibility of information leakage from two typical display devices with liquid crystal display (LCD). The compromising electromagnetic emanations are measured by log periodic antenna and wideband receiver in various distances. Frequency bands of leaked signal related to display on monitor exist in the range of several hundred megahertz with about ten megahertz bandwidth, which are different as display devices. Measured emanated signal is recovered as display by signal processing technique using software. In this process, timing parameters that necessary to composition of display are detected and clear recovered image is achieved by averaging multiple frames. The tendency of information leakage according to distance and display composition is analyzed by recovering emanated electromagnetic

The keyboard of a computer is often used to transmit sensitive data such as passwords. Because keyboards is electronic devices, it is forced to emit an electromagnetic wave, in the process of transmitting data. These compromising electromagnetic emanations disclose sensitive information, such as input keys on the keyboard [1]. In this paper, leaked electromagnetic radiation from the cable of the USB keyboard are measured by using a field probe. And recovery of the data was performed through it. Two kinds of keyboards were analyzed by signal processing algorithm. In conclusion, it is determined that the recovery of key information from electromagnetic emanations was possible for a total of 36 key (A to Z, 1 to zero).