Does Prompt-Tuning Language Model Ensure Privacy?

Original Paper: https://arxiv.org/abs/2304.03472

By: Shangyu Xie, Wei Dai, Esha Ghosh, Sambuddha Roy, Dan Schwartz, Kim Laine

Abstract:

Prompt-tuning has received attention as an efficient tuning method in the language domain, i.e., tuning a prompt that is a few tokens long, while keeping the large language model frozen, yet achieving comparable performance with conventional fine-tuning. Considering the emerging privacy concerns with language models, we initiate the study of privacy leakage in the setting of prompt-tuning. We first describe a real-world email service pipeline to provide customized output for various users via prompt-tuning. Then we propose a novel privacy attack framework to infer users' private information by exploiting the prompt module with user-specific signals. We conduct a comprehensive privacy evaluation on the target pipeline to demonstrate the potential leakage from prompt-tuning. The results also demonstrate the effectiveness of the proposed attack.

Summary Notes

Evaluating Privacy in Prompt-Tuning Language Models

Prompt-tuning language models (LMs) have become a cornerstone in making AI interactions more efficient and personalized.

Yet, as these models find their way into everyday applications, such as email services, concerns about user privacy have emerged. Can prompt-tuning really protect user privacy?

Understanding the Privacy Risks

Recent studies, particularly one focusing on a simulated email service, have highlighted a key issue with prompt-tuning LMs: they may leak private information.

This risk stems from the possibility of designing attacks to extract user data through the prompt module.

Background Concepts

• Fine-tuning: Adjusting a pre-trained model to a specific task, which is effective but resource-heavy.
• Prompting and Prompt-tuning: These methods add specific information to inputs to guide the model's output with minimal parameter changes.
• Privacy attacks, like membership inference and data reconstruction, aim to steal private data from models.

Study Focus: Email Service Pipeline

The study examined an email service using a LM for crafting replies:

• User Prompt Model: Generates user-specific prompts from user data using a Multi-Layer Perceptron (MLP).
• Base LM: The main language model that uses these prompts to personalize replies.

Privacy Attack Framework

The study presents a scenario where an attacker could extract private user information by manipulating the prompt-tuning model, particularly by analyzing the user prompt module.

Findings

Using data from a now-defunct company's email system, the study found:

• Prompt-tuning matches fine-tuning in accuracy and complexity.
• There's a clear risk of privacy breaches, with attackers capable of gathering private details like unique words from emails.

Implications

Prompt-tuning LMs bring computational benefits but also pose privacy risks, especially in sensitive applications.

This calls for a careful balance between efficiency and privacy, with improvements needed in prompt-tuning methods to better protect user data.

Ethical and Future Considerations

The study underscores the need for defensive strategies, such as differential privacy or dataset audits, to prevent the model from accidentally learning and leaking sensitive information.

Visuals and Comparisons

• Figure 1: Shows the email service's prompt-tuning architecture.
• Table 1: Compares performance metrics between fine-tuning and prompt-tuning, highlighting the research setup.

Key Takeaways

For organizations processing personal or sensitive data with LMs, this research is a critical reminder of the need to balance efficiency with privacy.

Enhancements in prompt-tuning methods are necessary to ensure robust data protection.

In summary, it's vital for AI engineers in enterprise environments to be aware of and address the privacy challenges posed by prompt-tuning LMs, advocating for or developing solutions that secure user data.