This paper proposed an external attack method for smartphone based on DTMF signal, which could attack effectively without the user being aware and without interaction with the smartphone. Firstly, it recorded some important keystroke ope-ration of user. Secondly, it performed double-threshold endpoint detection in time domain to extract the effective area of the signal. Thirdly, it converted the effective area to frequency domain by Goertzel algorithm for digital classification. Finally, all the keystroke data of the user were obtained by comparing the DTMF coding table. The experimental results show that the method can decipher more than 80% of the keystroke data under the condition of 10 dB signal-to-noise ratio and no interaction with the smartphone. In order to that, it proposed a defense method.

[2020-06-05] Printed Article /doc/2018.11.0893/v2