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Continuously understanding a user's location context in colloquial terms and the paths that connect the locations unlocks many opportunities for emerging applications. While extensive research effort has been made on efficiently tracking a user's raw coordinates, few attempts have been made to efficiently provide everyday contextual information about these(More)
Detecting visits to semantically meaningful places is important for many emerging mobile applications. We present PlaceSense, a place discovery algorithm suitable for mobile devices that exploits pervasive RF-beacons. By relying on separate mechanisms to detect entrance to and departure from a place and buffering overlapping data for subsequent visits, it(More)
Advances in mobile phone technology have allowed phones to become a convenient platform for real-time assessment of a participants health and behavior. AndWellness, a personal data collection system, uses mobile phones to collect and analyze data from both active, triggered user experience samples and passive logging of onboard environmental sensors. The(More)
Just as coordinate-oriented location-based applications have exploded recently with mapping services, new semantic location services will be critical for the next wave of killer applications. People are going to want everyday applications to have location-awareness that goes beyond simple numerical latitude and longitude. Loci is a new semantic location(More)
BACKGROUND/OBJECTIVES The accuracy of dietary recalls might be enhanced by providing participants with photo images of foods they consumed during the test period. SUBJECTS/METHODS We examined the feasibility of a system (Image-Diet Day) that is a user-initiated camera-equipped mobile phone that is programmed to automatically capture and transmit images to(More)
Location-Based Mobile Service (LBMS) is one of the most popular smartphone services. LBMS enables people to more easily connect with each other and analyze the aspects of their lives. However, sharing location data can leak people's privacy. We present PDVLoc, a controlled location data-sharing framework based on selectively sharing data through a Personal(More)
Recent secure code-update protocols for sensor networks have been based on asymmetric-cryptographic primitives such as digital signatures. Our approach, Castor, explores the feasibility of securing an existing code-update protocol, Deluge, using symmetric-cryptographic mechanisms that are more suited to the resource constraints of sensor nodes. Castor(More)
We present Castor, a secure code-update protocol for sensor networks that exploits symmetric cryptoystems. Through a synergistic combination of a one-way hash-chain, two one-way key-chains with the delayed disclosure of symmetric keys, and multiple message authentication codes (MACs), Castor enables untrusted sensor nodes to verify an update's authenticity(More)
This paper presents an assisted recall system, Rewind, that employs automatic image capture on mobile phones and filtering of images for end-user viewing. The usability of image-based assisted recall systems is limited by the large number of images through which the user must navigate. Rewind is a scalable system of everyday mobile phones and supporting web(More)
Dedication To my greatest parents · · · Hunchul Lee Soonok Kim To my loving grandparents · · · Jindoo Lee Jakyoung Huh To my uncle · · · Bonjin Byun To my best friend · · · Ga-Young Suh ii Acknowledgements I would like to express my sincere appreciation and gratitude to my advisor, Prof. Ortega, for his support and patience throughout my graduate studies at(More)