[Submitted on 14 Mar 2024]

Download a PDF of the paper titled What Was Your Prompt? A Remote Keylogging Attack on AI Assistants, by Roy Weiss and 3 other authors

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Abstract:AI assistants are becoming an integral part of society, used for asking advice or help in personal and confidential issues. In this paper, we unveil a novel side-channel that can be used to read encrypted responses from AI Assistants over the web: the token-length side-channel. We found that many vendors, including OpenAI and Microsoft, have this side-channel.

However, inferring the content of a response from a token-length sequence alone proves challenging. This is because tokens are akin to words, and responses can be several sentences long leading to millions of grammatically correct sentences. In this paper, we show how this can be overcome by (1) utilizing the power of a large language model (LLM) to translate these sequences, (2) providing the LLM with inter-sentence context to narrow the search space and (3) performing a known-plaintext attack by fine-tuning the model on the target model’s writing style.

Using these methods, we were able to accurately reconstruct 29\% of an AI assistant’s responses and successfully infer the topic from 55\% of them. To demonstrate the threat, we performed the attack on OpenAI’s ChatGPT-4 and Microsoft’s Copilot on both browser and API traffic.

Submission history

From: Yisroel Mirsky Dr. [view email]
Thu, 14 Mar 2024 09:38:12 UTC (5,400 KB)

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