The proliferation of smartphones has significantly facilitated people's daily life, and diverse and powerful embedded sensors make smartphone a ubiquitous platform to acquire and analyze data, which may also provide great potential for efficient human activity recognition. This paper presents a systematic performance analysis of motion-sensor behavior for human activity recognition via smartphones. Sensory data sequences are collected via smartphones, when participants perform typical and daily human activities. A cycle detection algorithm is applied to segment the data sequence for obtaining the activity unit, which is then characterized by time-, frequency-, and wavelet-domain features. Then both personalized and generalized model using diverse classification algorithms are developed and implemented to perform activity recognition. Analyses are conducted using 27 681 sensory samples from 10 subjects, and the performance is measured in the form of F-score under various placement settings, and in terms of sensitivity to user space, stability to combination of motion sensors, and impact of data imbalance. Extensive results show that each individual has its own specific and discriminative movement patterns, and the F-score for personalized model and generalized model can reach 95.95% and 96.26%, respectively, which indicates our approach is accurate and efficient for practical implementation.

The increasing use of smartphones as personal computing platforms to access personal information has stressed the demand for secure and usable authentication techniques, and for constantly protecting privacy. Smartphone sensors can measure users' unique behavioral characteristics when they interact with smartphones, based on different habits, gestures, and angle preferences of touch actions. This paper investigates the reliability and applicability of using motion-sensor behavior for active and continuous smartphone authentication across various operational scenarios, and presents a systematic evaluation of the distinctiveness and permanence properties of the behavior. For each sample of sensor behavior, kinematic information sequences are extracted and analyzed, which are characterized by statistic-, frequency-, and wavelet-domain features, to provide accurate and fine-grained characterization of users' touch actions. A Markov-based decision procedure, using one-class learning techniques, is developed and applied to the feature space for performing authentication. Analyses are conducted using the sensor data of 520 200 touch actions from 102 subjects across various operational scenarios. Extensive experiments show that motion-sensor behavior exhibits sufficient discriminability and stability for active and continuous authentication, and can achieve a false-rejection rate of 5.03% and a false-acceptance rate of 3.98%. Additional experiments on usability to operation length, sensitivity to application scenario, scalability to user size, contribution to different sensors, and response to behavior change are provided to further explore the effectiveness and applicability. We also implement an authentication system into the Android system that can react to the presence of the legitimate user.

Recent years have witnessed an exponential increase in the use of mobile and embedded devices. With the great success of deep learning in many fields, there is an emerging trend to deploy deep learning on mobile and embedded devices to better meet the requirement of real-time applications and user privacy protection. However, the limited resources of mobile and embedded devices make it challenging to fulfill the intensive computation and storage demand of deep learning models. In this survey, we conduct a comprehensive review on the related issues for deep learning on mobile and embedded devices. We start with a brief introduction of deep learning and discuss major challenges of implementing deep learning models on mobile and embedded devices. We then conduct an in-depth survey on important compression and acceleration techniques that help adapt deep learning models to mobile and embedded devices, which we specifically classify as pruning, quantization, model distillation, network design strategies, and low-rank factorization. We elaborate on the hardware-based solutions, including mobile GPU, FPGA, and ASIC, and describe software frameworks for mobile deep learning models, especially the development of frameworks based on OpenCL and RenderScript. After that, we present the application of mobile deep learning in a variety of areas, such as navigation, health, speech recognition, and information security. Finally, we discuss some future directions for deep learning on mobile and embedded devices to inspire further research in this area.

Federated learning facilitates the collaborative training of a global model among distributed clients without sharing their training data. Secure aggregation, a new security primitive for federated learning, aims to preserve the confidentiality of both local models and training data. Unfortunately, existing secure aggregation solutions fail to defend against Byzantine failures that are common in distributed computing systems. In this work, we propose a new secure and efficient aggregation framework, SEAR, for Byzantine-robust federated learning. Relying on the trusted execution environment, i.e., Intel SGX, SEAR protects clients’ private models while enabling Byzantine resilience. Considering the limitation of the current Intel SGX's architecture (i.e., the limited trusted memory), we propose two data storage modes to efficiently implement aggregation algorithms efficiently in SGX. Moreover, to balance the efficiency and performance of aggregation, we propose a sampling-based method to efficiently detect Byzantine failures without degrading the global model's performance. We implement and evaluate SEAR in a LAN environment, and the experiment results show that SEAR is computationally efficient and robust to Byzantine adversaries. Compared to the previous practical secure aggregation framework, SEAR improves aggregation efficiency by 4-6 times while supporting Byzantine resilience at the same time.

Behavior-based user authentication with pointing devices, such as mice or touchpads, has been gaining attention. As an emerging behavioral biometric, mouse dynamics aims to address the authentication problem by verifying computer users on the basis of their mouse operating styles. This paper presents a simple and efficient user authentication approach based on a fixed mouse-operation task. For each sample of the mouse-operation task, both traditional holistic features and newly defined procedural features are extracted for accurate and fine-grained characterization of a user's unique mouse behavior. Distance-measurement and eigenspace-transformation techniques are applied to obtain feature components for efficiently representing the original mouse feature space. Then a one-class learning algorithm is employed in the distance-based feature eigenspace for the authentication task. The approach is evaluated on a dataset of 5550 mouse-operation samples from 37 subjects. Extensive experimental results are included to demonstrate the efficacy of the proposed approach, which achieves a false-acceptance rate of 8.74%, and a false-rejection rate of 7.69% with a corresponding authentication time of 11.8 seconds. Two additional experiments are provided to compare the current approach with other approaches in the literature. Our dataset is publicly available to facilitate future research.

This paper is focused on the static output feedback control problem for a class of switched nonlinear systems with actuator faults. By means of the Takagi-Sugeno fuzzy model, the switched nonlinear plant is described by a family of switched fuzzy systems. Considering transmission failures may occur between controller and actuator, a reliable static output feedback controller against actuator faults is designed. Sufficient conditions are developed to guarantee the existence of the reliable static output feedback controller. Furthermore, an iterative algorithm is designed to determine the controller gains, whichavoidstheconservatismbroughtbythetraditionalsingular value decomposition method. To validate the effectiveness of the proposed approach, a numerical example is exploited and simulation results are also presented.