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With an increasing number of mobile devices equipped with screens and cameras, screen-camera communication (SCC) systems enable data exchange between devices conveniently and efficiently. By encoding data with spatial and temporal diversity on a screen, multiple users with a camera can receive data without setting up a wireless network. However, as the transmitter pushes the limits of increasing throughput with a high display rate, the receiver actually suffers from a low goodput caused by composite frames. Those frames cannot be decoded correctly with existing methods. To address this problem, we propose a reliable data recovery scheme named RescQR. In RescQR, a mixture separation scheme coupled with a dedicated frame border is proposed to separate composite frames. A Viterbi-based data recovery scheme is proposed to recover data from blurred regions in composite frames. Additionally, an auto-configuration method with the help of a front camera is proposed to adjust parameters automatically according to the estimated distance between the screen and the camera. Our prototype and experiments demonstrate that RescQR achieves a data goodput of 400+kbps even with standard QR codes, which significantly outperforms previous solutions.

ARM TrustZone is widely deployed on commercial-off-the-shelf mobile devices for secure execution. However, many Apps cannot enjoy this feature because it brings many constraints to App developers. Previous works have been proposed to build a secure execution environment for developers on top of TrustZone. Unfortunately, these works are still not fully-fledged solutions for mobile Apps, especially for emerging intelligent Apps. To this end, we propose LEAP, which is a lightweight developer-friendly TEE solution for mobile Apps. LEAP enables isolated codes to execute in parallel and access peripheral (e.g., mobile GPUs) with ease, flexibly manages system resources upon different workloads, and offers the auto DevOps tool to help developers prepare the codes running on it. We implement the LEAP prototype on the off-the-shelf ARM platform and conduct extensive experiments on it. The experimental results show that Apps can be adapted to run with LEAP easily and efficiently. Compared to the state-of-the-art work along this research line, LEAP can achieve an average 3.57× speedup in supporting intelligent Apps using mobile GPU acceleration.

Mobile edge computing (MEC) is proposed as an extension of cloud computing in the scenarios where the end devices desire better services in terms of response time. Because the edges are usually owned by individuals or small organizations with limited operation capabilities, the data on the edges are easily corrupted (due to external attacks or internal hardware failures). Therefore, it is essential to verify data integrity i the MEC. We propose two Integrity Checking protocols for the mobile Edge storage, called $\text{ICE}$ICE-basic and $\text{ICE}$ICE-batch. Our protocols allow a third-party verifier to check the data integrity on the edges without violating users’ data privacy and query pattern privacy. We rigorously prove the security and privacy guarantees of the protocols. In addition, we have investigated how to let the end devices cache some verification tags such that the communication cost between end devices and the cloud can be further reduced when a user connects to multiple edges in sequence. We have implemented a proof-of-concept system that runs $\text{ICE}$ICE, and extensive experiments are conducted to evaluate the performance of the proposed protocols. The theoretical analysis and experimental results demonstrate the proposed protocols are efficient both in computation and communication.