DR-Encoder: Encode Low-rank Gradients with Random Prior for Large Language Models Differentially Privately

Abstract

The emergence of the large language model (LLM) has shown its superiority in a wide range of disciplines, including language understanding and translation, relational logic reasoning, and even partial differential equations solving. The transformer is the pervasive backbone architecture for the foundation model construction. It is vital to research how to adjust the Transformer architecture to achieve an end-to-end privacy guarantee in LLM fine-tuning. This paper investigates three potential information leaks during a federated fine-tuning procedure for LLM (FedLLM). Based on the potential information leakage, we insert two-stage randomness into FedLLM to provide an end-to-end privacy guarantee solution. The first stage is to train a gradient auto-encoder with a Gaussian random prior based on the statistical information of the gradients generated by local clients. The second stage is fine-tuning the overall LLM with a differential privacy guarantee by adopting appropriate Gaussian noises. We show our proposed method's efficiency and accuracy gains with several foundation models and two popular evaluation benchmarks. Furthermore, we present a comprehensive privacy analysis with Gaussian Differential Privacy (GDP) and Renyi Differential Privacy (RDP).