The widely used devices(e.g.smartphones,recorders)equipped with microphones have posed a severe threat to confidential conversations.In this paper,we design an inaudible anti-eavesdropping method:UltraJam,to reduce th...The widely used devices(e.g.smartphones,recorders)equipped with microphones have posed a severe threat to confidential conversations.In this paper,we design an inaudible anti-eavesdropping method:UltraJam,to reduce the risk of unwanted and secret recordings.UltraJam uses the ultrasonic signal to mask conversation.By leveraging the nonlinear effect of microphone circuits,the adaptive ultrasonic signal can be recorded and demodulated into low-frequency which can effectively squash the sound.Based on the characteristics of the attenuation coefficient and frequency response,we construct a number of jamming signals with different bandwidths and designed a wideband signal injection array,meanwhile adaptively adjust the power at each bandwidth signal to cover more frequency bands and increase usage scenarios.To verify the security of the microphone jamming system,we also utilize several audio recovery methods to recover the raw signal from jamming noise.The experimental results show that less than 1% of the words are recognized in the jamming recording,and even with the audio recovery method,99% of the words still cannot be recognized in the recovered jamming recording.展开更多
In this Letter, a method based on the effects of imperfect oscillators in lasers is proposed to distinguish targets in continuous wave tracking lidar. This technique is based on the fact that each lidar signal source ...In this Letter, a method based on the effects of imperfect oscillators in lasers is proposed to distinguish targets in continuous wave tracking lidar. This technique is based on the fact that each lidar signal source has a specific influence on the phase noise that makes real targets from the false ones. A simulated signal is produced by complex circuits, modulators, memory, and signal oscillators. For example, a deception laser beam has an unequal and variable phase noise from a real target. Thus, the phase noise of transmitted and received signals does not have the same power levels and patterns. To consider the performance of the suggested method, the probability of detection（PD） is shown for various signal-to-noise ratios and signal-to-jammer ratios based on experimental outcomes.展开更多
基金supported by the Projects of the Natural Science Foundation of Qinghai Province(2021-ZJ-916)the National Natural Science Foundation of China(62202274).
文摘The widely used devices(e.g.smartphones,recorders)equipped with microphones have posed a severe threat to confidential conversations.In this paper,we design an inaudible anti-eavesdropping method:UltraJam,to reduce the risk of unwanted and secret recordings.UltraJam uses the ultrasonic signal to mask conversation.By leveraging the nonlinear effect of microphone circuits,the adaptive ultrasonic signal can be recorded and demodulated into low-frequency which can effectively squash the sound.Based on the characteristics of the attenuation coefficient and frequency response,we construct a number of jamming signals with different bandwidths and designed a wideband signal injection array,meanwhile adaptively adjust the power at each bandwidth signal to cover more frequency bands and increase usage scenarios.To verify the security of the microphone jamming system,we also utilize several audio recovery methods to recover the raw signal from jamming noise.The experimental results show that less than 1% of the words are recognized in the jamming recording,and even with the audio recovery method,99% of the words still cannot be recognized in the recovered jamming recording.
文摘In this Letter, a method based on the effects of imperfect oscillators in lasers is proposed to distinguish targets in continuous wave tracking lidar. This technique is based on the fact that each lidar signal source has a specific influence on the phase noise that makes real targets from the false ones. A simulated signal is produced by complex circuits, modulators, memory, and signal oscillators. For example, a deception laser beam has an unequal and variable phase noise from a real target. Thus, the phase noise of transmitted and received signals does not have the same power levels and patterns. To consider the performance of the suggested method, the probability of detection（PD） is shown for various signal-to-noise ratios and signal-to-jammer ratios based on experimental outcomes.
