OKEMOS - After a strict shepherd process, we are informed that our two papers are finally accepted by the 18th ACM Conference on Embedded Networked Sensor Systems (SenSys 2020). They are Patronus: Preventing Unauthorized Speech Recordings with Support for Selective Unscrambling and LiTag: Localization and Posture Estimation with Passive Visible Light Tags.

The widespread adoption and ubiquity of smart devices equipped with microphones unfortunately create many significant privacy risks. For example, Ukrainian prime minister offered his resignation after an unauthorized recording was leaked. In recent years, there have been several cases of people's conversations being secretly recorded, sometimes initiated by the device itself. Although some manufacturers are trying to protect users' privacy, to the best of our knowledge, there is not any effective technical solution available.

Patronus, an anti-secret audio recording system, emits ultrasonic noise, which cannot be sensed by human ears therefore doesn't affect normal talking but can be recorded by commercial off-the-shelf microphones with nonlinear effects, to scramble unauthorized devices. Scrambling noises could be canceled by authorized devices with the scramble pattern received from Wi-Fi/Bluetooth channels. It provides a possible solution to prevent unauthorized secret audio recording while allowing authorized recording.

Patronus system design: Scramble Transmitter transmits noises by sending two ultrasound waves to scramble the unauthorized device and the authorized device. The authorized device, however, receives the scramble pattern from the Scramble Transmitter through Wi-Fi/Bluetooth channel, therefore could cancel the scramble, hence getting a clear recording.

"The paper has been discussed deeply at the TPC meeting. The TPC members liked the idea of leveraging the nonlinear effects of microphones to prevent unauthorized recordings and allowing authorized ones", said the TPC summary. We believe Patronus could provide a practical solution to protect humans from secret recordings.

Many research efforts aim at providing precise item tracking or posture estimation with the UHF RFID technology. LiTag is a complementary technology to RFID, which achieves item identification, positioning, and posture estimation with a single surveillance camera. It makes use of widely deployed surveillance cameras, so you can just reuse them and don't have to deploy new RFID antennas and readers, thus providing a low-cost item tracking and posture estimation solution.

LiTag leverages birefringence to show different colors when we change the observation direction. After the camera capturing the LiTag, it firstly extracts the color sequence shown on the LiTag, then it derives the camera's position related to the LiTag, finally, the algorithm transforms the camera's relative position to the LiTag's position related to the camera with the geometry.

Litag design: Retroreflective part reflects all of the incident lights to the light source. After reflected lights passing through the polirizer P2, birefringence material, and polirizer P1, it shows a different color. The color will be changed among different incident angles.

"This is indeed an early attempt in its genre. Exciting potential challenges remain that need to be resolved. They demonstrate the rich potential for future work and extensions in the area", said the TPC shepherd. We believe that LiTag has a high potential to provide a low-cost and easy-to-use solution for ubiquitous localization and posture estimation with existing widely deployed cameras.

About ACM SenSys 2020

The 18th ACM Conference on Embedded Networked Sensor Systems (SenSys 2020) introduces a highly selective, single-track forum for research on systems issues of sensors and sensor-enabled smart systems, broadly defined. It is one of the top conferences in the field of computer network and internet of things. This conference provides an ideal venue to address research challenges facing the design, development, deployment, use, and fundamental limits of these systems. This year, due to the COVID-19 pandemic, the conference will be held online.