Biblio

This paper presents a photoplethysmography (PPG)-based continuous user authentication (CA) system, which especially leverages the PPG sensors in wrist-worn wearable devices to identify users. We explore the uniqueness of the human cardiac system captured by the PPG sensing technology. Existing CA systems require either the dedicated sensing hardware or specific gestures, whereas our system does not require any users' interactions but only the wearable device, which has already been pervasively equipped with PPG sensors. Notably, we design a robust motion artifacts (MA) removal method to mitigate the impact of MA from wrist movements. Additionally, we explore the characteristic fiducial features from PPG measurements to efficiently distinguish the human cardiac system. Furthermore, we develop a cardiac-based classifier for user identification using the Gradient Boosting Tree (GBT). Experiments with the prototype of the wrist-worn PPG sensing platform and 10 participants in different scenarios demonstrate that our system can effectively remove MA and achieve a high average authentication success rate over \$90%\$.

Domain Name System (DNS) had been recognized as an indispensable and fundamental infrastructure of current Internet. However, due to the original design philosophy and easy access principle, one can conveniently wiretap the DNS requests and responses. Such phenomenon is a serious threat for user privacy protection especially when an inside hacking takes place. Motivated by such circumstances, we proposed a ports distribution management solution to relieve the potential information leakage inside local DNS. Users will be able to utilize pre-assigned port numbers instead of default port 53. Selection method of port numbers at the server side and interactive process with corresponding end host are investigated. The necessary implementation steps, including modifications of destination port field, extension option usage, etc., are also discussed. A mathematical model is presented to further evaluate the performance. Both the possible blocking probability and port utilization are illustrated. We expect that this solution will be beneficial not only for the users in security enhancement, but also for the DNS servers in resources optimization.