Privacy Preserving Machine Learning — Course Page

Course taught by Aurélien Bellet
Master 2 Data Science, University of Lille

About this course

Personal data is being collected at an unprecedented scale by businesses and public organizations, driven by the progress of data science and AI. While training machine learning models on such personal or otherwise confidential data can be beneficial in many applications, this can also lead to undesirable (sometimes catastrophic) disclosure of sensitive information. In particular, machine learning models often contain precise information about individual data points that were used to train them. We must therefore deal with two conflicting objectives: maximizing the utility of the machine learning model while protecting the privacy of individuals whose data is used in the analysis. Unfortunately, recent years have shown that standard data anonymization techniques cannot reliably prevent leakage without largely destroying utility.

So how can we achieve both utility and privacy, or rather, obtain a good trade-off between the two? This course focuses on differential privacy, a mathematical definition of privacy which comes with rigorous guarantees as well as an algorithmic framework that allows the design of practical privacy preserving algorithms for data analytics and machine learning. In recent years, differential privacy has become the gold standard in various fields and has recently seen several real-world deployments by companies and government agencies.

This course will start by briefly illustrating why classic data anonymization schemes fail and how machine learning models and other aggregate statistics may leak sensitive information about individual data points. This will set the stage for differential privacy, which provides a principled probabilistic definition of what makes an algorithm private. We will introduce the formal definition of differential privacy and analyze its key properties. We will then turn to the design of differentially private algorithms in the standard centralized model, where a trusted curator wants to release the result of an analysis in a privacy-preserving way. We will introduce key algorithmic tools for privately answering simple numeric and non-numeric queries and prove their privacy and utility guarantees. These mechanisms will serve as building blocks to construct private machine learning algorithms. We will in particular focus on private empirical risk minimization with techniques based on randomly perturbing non-private models (output perturbation) or gradients (private stochastic gradient descent). Finally, we will consider the decentralized model of differential privacy, where individuals or data owners do not trust a curator to handle their private data. We will introduce local differential privacy, discuss intermediate trust models, and present applications to private federated learning where several data owners collaborate to train a model without sharing their data.

Lecture slides

Practical sessions in Python (Jupyter notebooks)


There will be two assignments. The final grade for the course will be the average over the two assignments.
  • Assignment 1 (lab session): Practical 3 will be graded. The deadline for sending your report is December 29. Refer to the notebook for detailed instructions.
  • Assignment 2 (paper presentation): By groups of 2 students, you will choose a research paper on privacy-preserving machine learning and write a report on the paper. The report should present the problem tackled in the paper, the main results and how they advance the previous literature, as well as a critical view of the merits and drawbacks of the proposed approach and a discussion of potential open questions. The report should be written in a way that is understandable by other students in the class who have not read the paper. Each group will also give a 15 minutes presentation to the class (followed by questions) on January 15. The report (in pdf format) should be sent to me by email no later than January 13.
    You can find below a list of suggested papers. Please coordinate among the class to avoid picking the same paper twice. You are welcome to suggest a paper which is not in this list, but you should confirm your choice with me first.
    • Abadi et al. Deep Learning with Differential Privacy. CCS 2016
    • Andrés et al. Geo-Indistinguishability: Differential Privacy for Location-Based Systems. CCS 2013
    • Erlingsson et al. RAPPOR: Randomized Aggregatable Privacy-Preserving Ordinal Response. CCS 2014
    • Feldman et al. Privacy Amplification by Iteration. FOCS 2018
    • Garfinkel et al. Issues Encountered Deploying Differential Privacy. WPES@CCS 2018
    • Geiping et al. Inverting Gradients - How easy is it to break privacy in federated learning? NeurIPS 2020
    • Jayaraman & Evans. Evaluating Differentially Private Machine Learning in Practice. USENIX Security 2019
    • McKenna & Sheldon. Permute-and-Flip: A new mechanism for differentially private selection. NeurIPS 2020
    • McMahan et al. Learning Differentially Private Recurrent Language Models. ICLR 2018
    • Papernot et al. Scalable Private Learning with PATE. ICLR 2018
    • Nasr et al. Comprehensive Privacy Analysis of Deep Learning: Passive and Active White-box Inference Attacks against Centralized and Federated Learning. S&P 2019
    • Sablayrolles et al. White-box vs Black-box: Bayes Optimal Strategies for Membership Inference. ICML 2020
    • Wang et al. Revisiting differentially private linear regression: optimal and adaptive prediction & estimation in unbounded domain. UAI 2018

Textbooks and survey papers