This is the bachelor thesis work of Jun Zhang done in State Key Laboratory of Networking and Switching Technology, supervised by Xiang Cheng.

With the development of information technology, popularity of smart devices and the extensive uses of sensors, the data volume in the world presents explosively increasing. Nowadays, our society has entered the era of big data. Set-valued data is one kind of classical big data. By mining the frequent items of users’ set-valued data, data aggregator can learn about the preferences of users, which can provide support for decisions. However, set-valued data contains a great number of sensitive information of users, directly reporting the frequent items and the corresponding counts or frequencies could lead to the leakage of users’ privacy. As the state-of-the-art privacy protection model, local differential privacy(LDP) provides a feasible solution for such problem.

In this paper, we propose a frequent items mining algorithm with ε-LDP, named Groupbased Frequent Items Mining (GFIM). The main idea of this algorithm is to first split the users randomly into two groups with the same size. Basing on the user data of the first group we gather the candidate set of possible frequent items, then we refine the candidate set using the user data of the second group. Finally, we obtain the estimated frequent items and the corresponding frequencies by combining the results of these two phases. This paper theoretically proves that GFIM satisfies ε-LDP. In addition, extensive experiments on synthetic dataset and real dataset demonstrate its effectiveness and superiority over existing method.

set-valued data, local differential privacy, frequent item mining

This repository is organized as follows:

• Code contains the source codes of the algorithm I designed GFIM.py, the baseline algorithm I reproduced according to one paper LDPMiner.py, the preprocessing script Prepocessing.py, my implementation of the building block algorithm Sampling_S-Hist.py, the script I used to synthesis the synthetic datasets SynthesizeData.py.

• Experiments contains all the results and intermediate results of the experiments I did as well as the figures I used in the paper.

• Papers contains the original paper of the baseline algorithm LDPMiner. This thesis work is inspired by this paper.

• Paper_JunZhang_Final.pdf is the final draft of the thesis paper.

• Presentations.pptx is the slides I used for thesis defence.

Due to the big size of the datasets, I didn't upload the datasets to this repo. The datasets I used in the experiments can be found here.

Translate the slides into English version. Date: Feb 13th， 2020