Analysis and Measurement on the Electromagnetic Compromising Emanations of Computer Keyboards

Keyboard is the main input device for computer systems. Electromagnetic waves will be emitted while the keyboards' working since they contain electronic components. These waves may generate electromagnetic interference, do harm to the operator's health and even reveal keystroke information thus bring information security problems. Focusing on the emanations concerned with information security, two different means that might compromise the keystroke information are analyzed in this paper. Data and clock signals that transfer the keyboard scan code to the computer are of critical importance. Besides, the ordinal scan routine of the computer keyboards will give out the column information of the pressed key. Then, a measurement experiment is designed to test the emanations of the keyboard. It is found that even the shielded keyboard will compromise the keystroke information, which indicates the keyboard with shielding measures do not give enough protection against information leakage via electromagnetic emanations.