Dali Zhu

WiseFi: Activity Localization and Recognition on Commodity Off-the-Shelf WiFi Devices

Most recently, activity localization and recognition has increasingly attracted significant attentions due to its broad range of applications to support smart devices. Pioneer systems based on WiFi signals usually require six to eight antennas to localize the activity while the commodity WiFi infrastructure does not meet this requirement. In addition, they also require the priori learning of wireless signals to recognize a pre-defined set of activities. In this paper, we present WiseFi, an activity localization and recognition system by leveraging fine-grained physical layer information on commodity off-the-shelf (COTS) WiFi devices. WiseFi harnesses the amplitude and the phase of Channel State Information (CSI), and the Angle-of-arrival (AOA) of blocked signals to localize and recognize human activity. The intuition behind WiseFi is that whenever the target occludes the incoming wireless signals, the power of AOA will drop in the same direction. Experimental results indicate that WiseFi can achieve comparable performance in activity localization and recognition on COTS WiFi devices.

WiN: Non-invasive Abnormal Activity Detection Leveraging Fine-Grained WiFi Signals

Abnormal activity detection has recently drawn significant research attention, because of its potential applications in providing critical and severe emergency information. Existing non-invasive activity detecting approaches rely on radio signals, wearable sensors or specialized hardware. Motivated by the observation that the amplitude and the phase information of channel state information CSI are highly sensitive to activity variation, we propose WiN, a non-invasive abnormal activity detection system, based on fine-grained physical layer channel state information, which is available from commercial off-the-shelf WiFi devices. We implement WiN and evaluate its performance in IEEE 802.11n devices. Extensive experiments in typical real-world environments demonstrate that WiN can achieve impressive performance in abnormal activity detection.

Analyzing Customer’s Product Preference Using Wireless Signals

Customer’s product preference provides how a customer collects products or prefers one collection over another. Understanding customer’s product preference can provide retail store owner and librarian valuable insight to adjust products and service. Current solutions offer a certain convenience over common approaches such as questionnaire and interviews. However, they either require video surveillance or need wearable sensor which are usually invasive or limited to additional device. Recently, researchers have exploited physical layer information of wireless signals for robust device-free human detection, ever since Channel State Information (CSI) was reported on commodity WiFi devices. Despite of a significant amount of progress achieved, there are few works studying customer’s product preference. In this paper, we propose a customer’s product preference analysis system, PreFi, based on Commercial Off-The-Shelf (COTS) WiFi-enabled devices. The key insight of PreFi is to extract the variance features of the fine-grained time-series CSI, which is sensitively affected by customer activity, to recognize what is the customer doing. First, we conduct Principal Component Analysis (PCA) to smooth the preprocessed CSI values since general denoising method is insufficient in removing the bursty and impulse noises. Second, a sliding window-based feature extraction method and majority voting scheme are adopted to compare the distribution of activity profiles to identify different activities. We prototype our system on COTS WiFi-enabled devices and extensively evaluate it in typical indoor scenarios. The results indicate that PreFi can recognize a few representative customer activity with satisfied accuracy and robustness.

A Dynamic Credible Factory Reset Mechanism of Personal Data in Android Device

Due to plenty of confidential and private information stored on the phone, the security of it has become more prominent increasingly. The private information storing on Android devices can be recovered easily even if it is reset by traditional data factory reset process. It is extremely unsafe and unreliable especially for the phone lent to others. In this paper, we proposed a dynamic credible factory mechanism of personal data in Android device to protect privacy. Not only it can allow users to factory reset the system quickly and safely, but it also thoroughly crushes application data files while applications are not deleted. The mechanism is based on a private file recognition algorithm that checks the properties of file tree dynamically proposed in the paper and credible erase on data blocks pointed from special inode of private files on the flash storage under the condition of no remounting and no rebooting. It aims to provide a more secure, fast crush method in Android system to prevent individual private data being recovered maliciously. We implemented our credible factory mechanism to evaluate their performance.

Digital Watermark Infrastructure for Information Protection

With reference to PKI-CA, the concept of DWI (Digital Watermarking Infrastructure) is formed. DWI marked network user activities by adding fingerprint attribute, in the form of generating digital fingerprint certificates. The structure and entities of DWI are defined; relevant general tasks between these entities are described; then DWI is compared and analyzed with PKI and IMPRIMATUR.

Multi-attribute Counterfeiting Tag Identification Protocol in Large-Scale RFID System

Counterfeiting products identification is the main application of RFID technology. Among all the RFID security problems, counterfeiting tag identification is an urgent issue with rapid growth of counterfeiters. In this paper, a multi-attribute counterfeiting tag identification protocol based on multi-dimension dynamic bloom filter in large-scale RFID system is proposed. Dynamic bloom filters for tag’s attributes: identity information ID and location information angle value, are first brought as criterion of counterfeiting tag identification. Different from previous probabilistic approaches, our protocol not only identifies unknown tags, but also first solves problem that counterfeiters hold the same ID with genuine ones. Furthermore, our protocol can detect and verify counterfeiting tags’ identity. Performance analysis shows that especially with huge amount of tags, our protocol can achieve higher identification efficiency with reasonable time cost.

An Efficient Approach of Integrating RFID and Vision Techniques in Object Surveillance System

With the automatically detecting and identifying ability, RFID has been widely used in object monitoring. However, due to the limited functionality of a single sensor, the RFID-based surveillance system doesnt do well in forensics and future tracking. To realize both real-time monitoring and automatically evidences extracting, a RFID and vision based object surveillance system is presented in this paper. Differing from other systems, we utilize motion detection results to control the video recording and tag reading. Then the stream processing and the complex event processing techniques are used to detect events of interest from the volume of raw RFID data in real time. Finally, an event-driven mechanism is proposed to integrate RFID and vision detected results. Also the effectiveness and efficiency of the proposed approach have been studied in this paper.

A Practical Scheme for Data Secure Transport in VoIP Conferencing

In the Multi-party VoIP conferencing system, it is important to provide properties of non-repudiation, unforgeable, and privacy. Previous work usually achieve these goals by using digital signature, TLS, IPsec, or other cryptographic tools. However, many approaches either compromise performance or lack of formal security proof, or both. In this work, we construct a practical Multi-party VoIP conferencing scheme based on the Boneh-Canetti-Halevi-Katz construction. Our work focus on the data secure transport stage, (i.e., we assume that the group session key is already distributed in the key distribution stage.). In comparison with previous work, our scheme gives a new paradigm for achieving properties of non-repudiation, unforgeable, and privacy simultaneously. The new paradigm avoids digital signature that have been shown time-consuming. On the other hand, our scheme is provable security. We prove the non-repudiation property in a formal way, and give proof sketches of unforgeable property and privacy property.

A Dynamic Supervisory Mechanism of Process Behaviors Based on Dalvik VM

The threats of smartphone security are mostly from the privacy disclosure and malicious chargeback software which deducting expenses abnormally. They exploit the vulnerabilities of previous permission mechanism to attack to mobile phones, and whats more, it might call hardware to spy privacy invisibly in the background. As the existing Android operating system doesnt support users the monitoring and auditing of system resources, a dynamic supervisory mechanism of process behavior based on Dalvik VM is proposed to solve this problem. The existing android system framework layer and application layer are modified and extended, and special underlying services of system are used to realize a dynamic supervisory on the process behavior of Dalvik VM. Via this mechanism, each process on the system resources and the behavior of each app process can be monitored and analyzed in real-time. It reduces the security threats in system level and positions that which process is using the system resource. It achieves the detection and interception before the occurrence or the moment of behavior so that it protects the private information, important data and sensitive behavior of system security. Extensive experiments have demonstrated the accuracy, effectiveness, and robustness of our approach.

Trusted access in wireless network on mutual interactive authentication mechanism

The wireless networking is faced with a large number of attacks such as ARP spoofing, MITM attack and rogue AP. If the wireless terminal and AP can be verified before the wireless terminal accesses network, it can provide higher security at the source. In this paper, we propose a trusted access in wireless network on mutual interactive authentication mechanism of dynamic secret key. The proposed algorithm consists of the verification on the mobile client registering and accessing to the network. It contains the two-way authentication between AP and the mobile terminal. We implement our trusted access technique extensively on commercially available AP to evaluate the performance. It has demonstrated the accuracy, effectiveness, scalability and robustness of our approach in preventing attacks.