JamSys: Coverage Optimization of a Microphone Jamming System Based on Ultrasounds

Abstract

With the development of digital devices, the recording process has become increasingly easier to conduct. However, the portability of the recording devices has also made recording difficult to monitor. If private conversations are illegally recorded, it will cause serious secret-leakage events. Therefore, it is imperative to prevent unauthorized recordings. Recent works have demonstrated that the nonlinearity effect of microphones can be leveraged to interfere with microphone recording using ultrasounds. However, an ultrasonic array has a limited jamming area. The design of an anti-recording system composed of multiple ultrasonic arrays remains to be addressed. In this paper, a jamming system, JamSys, is presented to prevent eavesdropping in a given region. We propose a new scheme composed of the angle coverage model and the modified harmony search algorithm (MHSA) to optimize the deployment of ultrasonic arrays, which achieves the maximum jamming area with the given number of arrays. In the simulation and experiments, three different optimization algorithms, the MHSA, the genetic algorithm (GA), and the regular coverage algorithm (RCA) are compared. The MHSA is demonstrated to provide the best results.INDEX TERMS Privacy protection, anti-recording, microphones, ultrasounds, optimization algorithms. I. INTRODUCTIONElectronic eavesdropping is a means of stealing important information. Recording is a typical type of eavesdropping. Due to the small size of recording devices, attackers can easily record secret information in confidential meetings and private conversations. Therefore, protecting confidential and private activities from illegal recording is very important for personal communication secrets, commercial trade, and even national security.The current protection methods can be categorized into two broad categories: detection and jamming techniques. The detection techniques rely on metal detectors or X-ray scanners to detect electronic devices. However, such techniques are unreasonable if electronic devices are not allowed in some situations, such as cinemas. Some electronic devices, such as laptops, cannot be blocked from being carried because they may be used in meetings. The above drawbacks limit the use of detection techniques.The associate editor coordinating the review of this manuscript and approving it for publication was Cristina Rottondi.

Taxonomy and Challenges of Out-of-Band Signal Injection Attacks and Defenses

“…In other words, the same source of vulnerability which can be used to destabilize [10] and control [13], [34], [43] gyroscopes and accelerometers can be used for covert channel communication [171], [172], tracking [173], and speaker identification [174], [175]. Similarly, instead of using microphone non-linearities for command injections [11], [55], [134], Shen et al [177] and Chen et al [178] leveraged them to protect users' privacy by jamming nearby recording devices.…”

SoK: A Modularized Approach to Study the Security of Automatic Speech Recognition Systems

“…In [27], [90], [91], [97], [101], [138], [139], [146], the authors exploit the non-linearity vulnerability of the microphones in IVC devices. In particular, the adversary can craft malicious voice commands at inaudible frequency by exploiting non-linearity in the demodulation of current microphone technology.…”

“…Specifically, they find that many popular speech recognition systems utilize MFCC to extract acoustic features for analysis and decoding. Therefore, they propose to mangle a malicious voice command signal, so that it can preserve [27], [53], [90], [91], [97], [101], [104], [138], [139], [142], [146] Sensor enough MFCC acoustic features for the target speech recognition systems to recognize their desired command, but remain difficult for human being to interpret. They demonstrate their attacks against both white box (CMU Sphinx) and black box (Google Now) speech recognition systems, and the human perception study shows the adversarial audio is almost uninterpretable to human being.…”