Differentially Private Release of Hierarchical Origin/Destination Data with a TopDown Approach

This repository contains the code for the paper "Differentially Private Release of Hierarchical Origin/Destination Data with a TopDown Approach"

To run the code, you need to install a conda environment using the environment.yml file

conda env create -f environment.yml

Then, activate the environment

conda activate top-down

Data Pre-Processing

Generate the synthetic datasets

To generate the synthetic dataset run the shell files into /run_command/run_preprocess/ folder. Inside you will find two shell files, one for the binary tree, the other for the random tree. You can change the parameters of the synthetic dataset in the shell files, like the sparsity, the number of levels, the seed for the randomizer. ```bash cd runcommand/runpreprocess

chmod +x generatesyntheticdatasetwithbinarybranching.sh chmod +x generatesyntheticdatasetwithrandombranching.sh

./generatesyntheticdatasetwithbinarybranching.sh ./generatesyntheticdatasetwithrandombranching.sh

```

Generate the real dataset

It is necessary to download the dataset from ISTAT website.

https://www.istat.it/storage/cartografia/matrici_pendolarismo/matrici-pendolarismo-sezione-censimento-2011.zip

This files needs to be inserted into the /preprocess_data directory. The file then needs to be unzipped, then, it is sufficient to run the python script

bash cd preprocess_data python preprocess_ISTAT_data.py

This generates a data folder containing the datasets.

Experiments

The experiment on the Italian dataset can be run using the shell file /run_command/Italy.sh

bash cd run_command chmod +x Italy.sh ./Italy.sh The experiments on the synthetic dataset can be run using the shell file /run_command/all_synthetic.sh

bash cd run_command chmod +x all_synthetic.sh ./all_synthetic.sh

The experiments will generate new results.pickle files in the /results folder. The results presented in the paper are already present in the folder as results_1.pickle. To plot the results, you can use the jupyter notebook in the /notebooks folder.

Note

1. The experiments take a long time to run. The Italy dataset takes about 2 hours per experiments while the synthetic datasets take about 1 hour. By default, 10 indipendent experiments are run for each dataset, so the total time surpasses a day. I recommend to run just for a couple of experiments. It is sufficient to change th shell files. Example on Italy dataset python Italy_experiments.py --delta 1e-8 --show-tqdm --epsilons 0.1,1,10 --num-experiments 10 --final-level 6 \ --file-path "../data/Italy" \ --save-path "../results/Italy" Change to python Italy_experiments.py --delta 1e-8 --show-tqdm --epsilons 0.1,1,10 --num-experiments 1 --final-level 6 \ --file-path "../data/Italy" \ --save-path "../results/Italy"

2. Even though our paper investigates theoretically how to generalize the algorithm for different sensitivities, our implementation works only for the case where each user contributes to a single trip, and the neighboring relation is for bounded differential privacy. This is the case investigated in our experimental section.