With the recent rapid advancements in the Internet-of-Things (IoT), one of the applications being developed is that of smart door lock (SDL) systems. SDL are intended to offer high security, easy access and easy sharing. Unlike existing SDL solutions that mostly use biometrics or crunched RF spectrum, we uniquely propose to use Infrared (IR) optical wireless signal (OWS) using IR light emitting diode (LED) of smartphones. We designed and developed a complete system of Android smartphone app including physical layer encoding, a cloud server and programmable hardware prototypes using Arduino as well as Raspberry Pi. Optlock includes multi-level security schemes including user registration, authentication and authorization using one-time-password (OTP). Our extensive experiments show 100% accuracy with 1.33 kbps of average data rate is achieved up to 20 meters of distance between a smartphone and a lock. It allows convenient remote access, easy access control and sharing as well as high security.

As recent smartphone technologies in software and hardware keep on improving, many smartphone users envision to perform various mission critical applications on their smart-phones that were previously accomplished by using PCs. Hence, smartphone authentication has become one of the most critical security issues. Due to the relatively small smartphone form factor, the traditional user id and password typed authentication is considered as an inconvenient and time-taking approach. Taking advantage of various sensor technologies of smartphones, alternative authentication methods such as pattern, gesture, finger print, and face recognition have been actively researched. However, those authentication methods still pose one of speed, reliability, and usability issues. They are especially not suitable for the users in rugged conditions and with physical challenges. In this paper, we evaluate existing alternative smartphone authentication approaches in various usage scenarios to propose ambient light sensor based authentication for smartphones. We have designed and prototyped a challenge-based programmable Fast, Inexpensive, Reliable, and Easy-to-use (FIRE) hardware authentication token. FIRE token uses an onboard LED to transmit passwords via an Optical Wireless Signal (OWS) to the smartphone that captures, and interprets it via its ambient light sensor. FIRE token is a part of the challenge-response technique in the Inverse Dual Signature (IDS) that we designed to facilitate a multi-factor authentication for the mission critical smartphone applications. Our experiments validate that FIRE can authenticate a user on a smartphone in a simple, fast, and reliable way without compromising the security quality and user experience.

As smartphones gain their popularity, vulnerable road users (VRUs) are increasingly distracted by activities with their devices such as listening to music, watching videos, texting or making calls while walking or bicycling on the road. In spite of the development of various high-tech Car-to-Car (C2C) and Car-to-Infrastructure (C2I) communications for enhancing the traffic safety, protecting such VRUs from vehicles still relies heavily on traditional sound warning methods. Furthermore, as smartphones continue to become highly ubiquitous, VRUs are increasingly oblivious to safety related warning sounds. A traffic accident study shows the number of headphone-wearing VRUs involved in roadside accidents has increased by 300% in the last 10 years. Although recently a few Car2Pedestrian-communication methods have been proposed by various car manufacturers, their practical usage is limited, as they mostly require special communication devices to cope with the wide range of mobility, and also assume VRUs' active attention to the communication while walking. We propose a smartphone-based Car2X-communication system, named WiFi-Honk, which can alert the potential collisions to both VRUs and vehicles in order to especially protect the distracted VRUs. WiFi-Honk provides a practical safety means for the distracted VRUs without requiring any special device using WiFi of smartphone. WiFi-Honk removes the WiFi association overhead using the beacon stuffed WiFi communication with the geographic location, speed, and direction information of the smartphone replacing its SSID while operating in WiFi Direct/Hotspot mode, and also provides an efficient collision estimation algorithm to issue appropriate warnings. Our experimental and simulation studies validate that WiFi-Honk can successfully alert VRUs within a sufficient reaction time frame, even in high mobility environments.

Despite various high-tech Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) communications that have been developed for enhancing traffic safety, protecting vulnerable road users (VRU), such as pedestrians and bicyclists from the vehicles and trains still heavily relies on the traditional sound warning method. Furthermore, as smart devices continue to become highly ubiquitous, the more VRU are shutting out the safety related warning sounds. A traffic accident study shows the number of headphone-wearing VRU involved in roadside accidents has tripled since 2004. Although recently a few Car2Pedestrian communication methods have been proposed by various car makers, their practical usage is still in question. They assume VRUs' active attention to the communication while walking, and also mostly require special communication devices to cope with the wide range of mobility. In this paper, we propose a smartphone based Car2X communication system, named WiFiHonk that can alert of potential collisions to both VRU and vehicles in order to especially protect the distracted VRU. WiFiHonk provides a practical safety means for the distracted VRU without requiring any special device using the WiFi of a smart device. It is novel in that it removes the WiFi association overhead using the beacon stuffed WiFi communication and also provides an efficient collision estimation algorithm to issue appropriate warnings. Our experimental and simulation studies validate that WiFiHonk can successfully alert the VRU within a sufficient reaction time frame.

The fast growing popularity of smartphones and tablets enables us the use of various intelligent mobile applications. As many of those applications require position information, a smart mobile device provides positioning methods such as GPS, WiFi, or Cell-ID based positioning services. However, those positioning methods have different characteristics of energy efficiency, accuracy, and service availability. In this paper, we present an Energy- Efficient Cooperative and Opportunistic Positioning System (ECOPS) for heterogeneous mobile devices. ECOPS facilitates mobile devices with estimated locations using WiFi in cooperation with a few available GPS broadcasting devices, in order to achieve high energy efficiency and accuracy within available budget constraints. ECOPS estimates the location using heterogeneous positioning services and the combination methods including a received signal strength indicator, 2D trilateration, and available power measurement of mobile devices. The evaluation shows that ECOPS significantly reduces energy consumption and achieves the good accuracy of a location.