Introduction

The popularity of recording equipment leads to serious privacy and security issues. Due to their small sizes, they can be used to perform unauthorized audio recording without people’s awareness. Already, reports show that microphones in webcams are used to monitor daily conversation by criminals, which poses severe ricks against personal privacy. To remit the situation, we therefore propose an EMI-signal-injection based approach to prevent unauthorized audio recording, with a focus on recording pens.

Our EMI injection scheme can achieve anti-recording by placing a few EMI injectors in various sounding environments. The EMI injectors emit carefully crafted signals at the vulnerable frequency of the devices, whereby the injected signals can completely overwrite the recorded audios that are stimulated by the sounds in the environment. Our results show that the EMI injection scheme is effective against several recording devices.