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1. PrivTrace: Differentially Private Trajectory Synthesis by Adaptive Markov Models

   Wang, Haiming; Zhang. Zhikun; Wang, Tianhao; He, Shibo; Backes, Michael; Chen, Jiming; Zhang, Yang (August 2023, USENIX)

   Publishing trajectory data (individual’s movement information) is very useful, but it also raises privacy concerns. To handle the privacy concern, in this paper, we apply differential privacy, the standard technique for data privacy, together with Markov chain model, to generate synthetic trajectories. We notice that existing studies all use Markov chain model and thus propose a framework to analyze the usage of the Markov chain model in this problem. Based on the analysis, we come up with an effective algorithm PrivTrace that uses the first-order and second-order Markov model adaptively. We evaluate PrivTrace and existing methods on synthetic and real-world datasets to demonstrate the superiority of our method. 

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2. Reliable generation of privacy-preserving synthetic electronic health record time series via diffusion models

   https://doi.org/10.1093/jamia/ocae229  

   Tian, Muhang; Chen, Bernie; Guo, Allan; Jiang, Shiyi; Zhang, Anru R (September 2024, Journal of the American Medical Informatics Association)

   Electronic health records (EHRs) are rich sources of patient-level data, offering valuable resources for medical data analysis. However, privacy concerns often restrict access to EHRs, hindering downstream analysis. Current EHR deidentification methods are flawed and can lead to potential privacy leakage. Additionally, existing publicly available EHR databases are limited, preventing the advancement of medical research using EHR. This study aims to overcome these challenges by generating realistic and privacy-preserving synthetic EHRs time series efficiently. Materials and Methods: We introduce a new method for generating diverse and realistic synthetic EHR time series data using denoizing diffusion probabilistic models. We conducted experiments on 6 databases: Medical Information Mart for Intensive Care III and IV, the eICU Collaborative Research Database (eICU), and non-EHR datasets on Stocks and Energy. We compared our proposed method with 8 existing methods. Results: Our results demonstrate that our approach significantly outperforms all existing methods in terms of data fidelity while requiring less training effort. Additionally, data generated by our method yield a lower discriminative accuracy compared to other baseline methods, indicating the proposed method can generate data with less privacy risk. Discussion: The proposed model utilizes a mixed diffusion process to generate realistic synthetic EHR samples that protect patient privacy. This method could be useful in tackling data availability issues in the field of healthcare by reducing barrier to EHR access and supporting research in machine learning for health. Conclusion: The proposed diffusion model-based method can reliably and efficiently generate synthetic EHR time series, which facilitates the downstream medical data analysis. Our numerical results show the superiority of the proposed method over all other existing methods. 

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3. Differentially Private Synthetic Data via Foundation Model APIs 2: Text

   Xie, Chulin; Lin, Zinan; Backurs, Arturs; Gopi, Sivakanth; Yu, Da; Inan, Huseyin A; Nori, Harsha; Jiang, Haotian; Zhang, Huishuai; Lee, Yin Tat; et al (July 2024, International Conference on Machine Learning (ICML 2024))

   Text data has become extremely valuable due to the emergence of machine learning algorithms that learn from it. A lot of high-quality text data generated in the real world is private and therefore cannot be shared or used freely due to privacy concerns. Generating synthetic replicas of private text data with a formal privacy guarantee, i.e., differential privacy (DP), offers a promising and scalable solution. However, existing methods necessitate DP finetuning of large language models (LLMs) on private data to generate DP synthetic data. This approach is not viable for proprietary LLMs (e.g., GPT-3.5) and also demands considerable computational resources for open-source LLMs. Lin et al. (2024) recently introduced the Private Evolution (PE) algorithm to generate DP synthetic images with only API access to diffusion models. In this work, we propose an augmented PE algorithm, named AUGPE, that applies to the complex setting of text. We use API access to an LLM and generate DP synthetic text without any model training. We conduct comprehensive experiments on three benchmark datasets. Our results demonstrate that AUGPE produces DP synthetic text that yields competitive utility with the SOTA DP finetuning baselines. This underscores the feasibility of relying solely on API access of LLMs to produce high-quality DP synthetic texts, thereby facilitating more accessible routes to privacy-preserving LLM applications. Our code and data are available at https://github.com/AI-secure/aug-pe. 

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4. Knowledge Infusion in Privacy Preserving Data Generation

   Kotal, Anantaa; Das, Nilanjana; Joshi, Anupam (August 2023, KDD Workshop on Knowledge-infused Learning, 29TH ACM SIGKDD)

   Security monitoring is crucial for maintaining a strong IT infrastructure by protecting against emerging threats, identifying vulnerabilities, and detecting potential points of failure. It involves deploying advanced tools to continuously monitor networks, systems, and configurations. However, organizations face challenges in adapting modern techniques like Machine Learning (ML) due to privacy and security risks associated with sharing internal data. Compliance with regulations like GDPR further complicates data sharing. To promote external knowledge sharing, a secure and privacy-preserving method for organizations to share data is necessary. Privacy-preserving data generation involves creating new data that maintains privacy while preserving key characteristics and properties of the original data so that it is still useful in creating downstream models of attacks. Generative models, such as Generative Adversarial Networks (GAN), have been proposed as a solution for privacy preserving synthetic data generation. However, standard GANs are limited in their capabilities to generate realistic system data. System data have inherent constraints, e.g., the list of legitimate I.P. addresses and port numbers are limited, and protocols dictate a valid sequence of network events. Standard generative models do not account for such constraints and do not utilize domain knowledge in their generation process. Additionally, they are limited by the attribute values present in the training data. This poses a major privacy risk, as sensitive discrete attribute values are repeated by GANs. To address these limitations, we propose a novel model for Knowledge Infused Privacy Preserving Data Generation. A privacy preserving Generative Adversarial Network (GAN) is trained on system data for generating synthetic datasets that can replace original data for downstream tasks while protecting sensitive data. Knowledge from domain-specific knowledge graphs is used to guide the data generation process, check for the validity of generated values, and enrich the dataset by diversifying the values of attributes. We specifically demonstrate this model by synthesizing network data captured by the network capture tool, Wireshark. We establish that the synthetic dataset holds up to the constraints of the network-specific datasets and can replace the original dataset in downstream tasks. 

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5. Privacy-Preserving Data Sharing in Agriculture: Enforcing Policy Rules for Secure and Confidential Data Synthesis

   https://doi.org/10.1109/BigData59044.2023.10386276  

   Kotal, Anantaa; Elluri, Lavanya; Gupta, Deepti; Mandalapu, Varun; Joshi, Anupam (December 2023, IEEE International Conference on Big Data)

   Big Data empowers the farming community with the information needed to optimize resource usage, increase productivity, and enhance the sustainability of agricultural practices. The use of Big Data in farming requires the collection and analysis of data from various sources such as sensors, satellites, and farmer surveys. While Big Data can provide the farming community with valuable insights and improve efficiency, there is significant concern regarding the security of this data as well as the privacy of the participants. Privacy regulations, such as the European Union’s General Data Protection Regulation (GDPR), the EU Code of Conduct on agricultural data sharing by contractual agreement, and the proposed EU AI law, have been created to address the issue of data privacy and provide specific guidelines on when and how data can be shared between organizations. To make confidential agricultural data widely available for Big Data analysis without violating the privacy of the data subjects, we consider privacy-preserving methods of data sharing in agriculture. Synthetic data that retains the statistical properties of the original data but does not include actual individuals’ information provides a suitable alternative to sharing sensitive datasets. Deep learning-based synthetic data generation has been proposed for privacy-preserving data sharing. However, there is a lack of compliance with documented data privacy policies in such privacy-preserving efforts. In this study, we propose a novel framework for enforcing privacy policy rules in privacy-preserving data generation algorithms. We explore several available agricultural codes of conduct, extract knowledge related to the privacy constraints in data, and use the extracted knowledge to define privacy bounds in a privacy-preserving generative model. We use our framework to generate synthetic agricultural data and present experimental results that demonstrate the utility of the synthetic dataset in downstream tasks. We also show that our framework can evade potential threats, such as re-identification and linkage issues, and secure data based on applicable regulatory policy rules. 

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