  The wide applicability and adaptability of generative large language models
(LLMs) has enabled their rapid adoption. While the pre-trained models can
perform many tasks, such models are often fine-tuned to improve their
performance on various downstream applications. However, this leads to issues
over violation of model licenses, model theft, and copyright infringement.
Moreover, recent advances show that generative technology is capable of
producing harmful content which exacerbates the problems of accountability
within model supply chains. Thus, we need a method to investigate how a model
was trained or a piece of text was generated and what their pre-trained base
model was. In this paper we take the first step to address this open problem by
tracing back the origin of a given fine-tuned LLM to its corresponding
pre-trained base model. We consider different knowledge levels and attribution
strategies, and find that we can correctly trace back 8 out of the 10 fine
tuned models with our best method.
