  AI-powered chatbots (ChatGPT, Claude, etc.) require users to create an
account using their email and phone number, thereby linking their personally
identifiable information to their conversational data and usage patterns. As
these chatbots are increasingly being used for tasks involving sensitive
information, privacy concerns have been raised about how chatbot providers
handle user data. To address these concerns, we present ProxyGPT, a
privacy-enhancing system that enables anonymous queries in popular chatbot
platforms. ProxyGPT leverages volunteer proxies to submit user queries on their
behalf, thus providing network-level anonymity for chatbot users. The system is
designed to support key security properties such as content integrity via
TLS-backed data provenance, end-to-end encryption, and anonymous payment, while
also ensuring usability and sustainability. We provide a thorough analysis of
the privacy, security, and integrity of our system and identify various future
research directions, particularly in the area of private chatbot query
synthesis. Our human evaluation shows that ProxyGPT offers users a greater
sense of privacy compared to traditional AI chatbots, especially in scenarios
where users are hesitant to share their identity with chatbot providers.
Although our proof-of-concept has higher latency than popular chatbots, our
human interview participants consider this to be an acceptable trade-off for
anonymity. To the best of our knowledge, ProxyGPT is the first comprehensive
proxy-based solution for privacy-preserving AI chatbots. Our codebase is
available at https://github.com/dzungvpham/proxygpt.
