Differentially Private Latent Diffusion Models

22 Sept 2023 (modified: 11 Feb 2024)Submitted to ICLR 2024EveryoneRevisionsBibTeX
Primary Area: societal considerations including fairness, safety, privacy
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Keywords: differential privacy, latent diffusion models, generative modelling, synthetic image generation
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Abstract: Diffusion models (DMs) are widely used for generating high-quality high- dimensional images in a non-differentially private manner. However, due to the notoriously slow training process of DMs, applying differential privacy (DP) to the training routine requires adding large amounts of noise, yielding poor-quality generated images. To address this challenge, recent papers suggest pre-training DMs with public data, then fine-tuning them with private data using DP-SGD for a relatively short period. In this paper, we aim to further improve the current state of DMs with DP by adopting the Latent Diffusion Models (LDMs). LDMs are equipped with powerful pre-trained autoencoders that map the high-dimensional pixels into lower-dimensional latent representations, where DMs are then trained in the latent space, yielding a more efficient and fast training. In our algorithm, DP-LDMs, rather than fine-tuning the entire DMs, we fine-tune only the attention modules of LDMs at varying layers with privacy-sensitive data, reducing the num- ber of trainable parameters by approximately 96% compared to fine-tuning the entire DMs. The smaller parameter space to fine-tune with DP-SGD helps our algo- rithm to achieve a new state-of-the-art results in several public-private benchmark data pairs. Our approach also allows us to generate high-dimensional images (256 by 256) and those conditioned on text prompts with differential privacy, which have not been attempted yet in DP literature. Our approach provides a promising direction for training more powerful, yet training-efficient differentially private DMs that can produce high-quality high-dimensional synthetic images.
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Submission Number: 4377
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