H Welcome

Hi, I am Xi. I graduated from National University of Singapore with Double Degree of Applied Mathematics and Computer Science.

I currently completed my PhD program in Computer Science with Prof. Ashwin Machanavajjhala. I will join the Cheriton School of Computer Science at University of Waterloo as an assistant professor (my new site ).


Contact Information
Duke University
Dept. of Computer Science
LSRC Building D101
308 Research Drive, Campus Box 90129
Durham, NC 27708
P: (919) 660-4007


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Blowfish Privacy: Tuning Privacy-Utility Trade-offs using Policies

Collaborators: Ashwin Machanavajjhala and Bolin Ding · This research aims to provide ways for trading-off the privacy of individuals in a statistical database for the utility of downstream analysis of data. We present a novel class of privacy definitions - Blowfish privacy, which offers a rich interface to specify this trade-off. We show significant utility improvements for k-means clustering, releasing cumulative histograms and answering range queries with mechanisms under Blowfish privacy in comparison to their differentially private counterparts. (more details)

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Differentially Private Trajectory Synthesis

Collaborators: Ashwin Machanavajjhala, Divesh Srivastava, Cecilia M. Procopiuc, Graham Cormode · This research considers methods to publish locations traces with differential privacy guarantee. Our approach involves modeling the location traces as top-k mobility patterns for a bounded sensitivity, and sampling location traces from a noisy semi-Markov model learned on the top-k patterns. We present pruning strategies and efficient algorithms to post-process the noisy model which has an unbalanced hierarchical structure and to synthesize locations traces closer to the real datasets.(more details)

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Coloring Privacy

This project has studied privacy in mobile-social system from another angle, visualization. Visualization creates images, graphics or animations to enhance people's understanding of information....(more details)

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GPU Computing

Driven by the high computation power and affordability of Graphics Processing Units, known as GPU, we would like to explore the new role of GPU as a more general purpose processor for scientific and engineering applications.... (more details)




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Ashwin Machanavajjhala, Xi He, "Provably privacy for mobility data", Springer Handbook on Mobile
Data Privacy, 2017

Xi He, Ashwin Machanavajjhala, Cheryl Flynn, Divesh Srivastava, "composing differential privacy and secure
computation: A case study on scaling private record linkage", CCS 2017 link

Ashwin Machanavajjhala, Xi He, Michael Hay, "Differential privacy in the wild: a tutorial on current practices
& open challenges", SIGMOD 2017 link

Xi He, Nisarg Raval, Ashwin Machanavajjhala, "A Demonstration of VisDPT: visual exploration of differentially
private trajectories", VLDB 2016 (BEST DEMO AWARD) pdf

Ashwin Machanavajjhala, Xi He, Michael Hay, "Differential privacy in the wild: a tutorial on current practices
& open challenges", VLDB 2016 link

Xi He, Graham Cormode, Ashwin Machanavajjhala, Cecilia M. Procopiuc, Divesh Srivastava, "DPT: Differentially
private trajectory synthesis using hierarchical reference systems", VLDB 2015 pdf code

Xi He, Ashwin Machanavajjhala, Bolin Ding, "Blowfish Privacy: Tuning Privacy-Utility Trade-offs using Policies",
SIGMOD 2014 pdf

Y.C. Tay, Xuanran Zong, Xi He, "An Equation-Based Heap Sizing Rule",
Performance Evaluation 70, 11 (Nov. 2013), 948–964.



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I like dancing, martial arts, basketball, swimming, web designs, movies...