Information Recover Based On Compromising Electromagnetic Emanations Of Keyboard

Computer keyboards are often used to enter a number of confidential data such as passwords. The leaking of this information will thread to the security of password-based authentication system. The TEMPEST attack is an effective side-channel attack, which base on the compromising electromagnetic emanations of keyboard. The mechanism of compromising electromagnetic emanations of keyboard is similar to other information technology devices. Based on the research of compromising electromagnetic emanations mechanism of information technology devices, we analysis of the compromising electromagnetic emanations mechanism of keyboard. The structure of the keyboards contain electronic components leading to the keyboard eventually emit electromagnetic waves to the external. The electromagnetic radiation signals which are emitted by these keystrokes could reveal sensitive information. This signal's frequency range is fixed and time-domain characteristic is obvious. We collected this signal of PS/ 2 and USB keyboards by using antenna and oscilloscope, and compared the compromising electromagnetic emanations of different distances and keystrokes. Meanwhile, according to the characteristics of compromising electromagnetic emanations and PS/2 protocol, we designed an algorithm to recover the information of keystrokes. Based on the algorithm and the waveform data acquired from oscilloscope, we actual design a keystrokes recovery system which can accurately restore the information of keystrokes. This verifies the feasibility of side-channel attack to keyboards through compromising electromagnetic emanations of keyboards.