DP2Unlearning: An efficient and guaranteed unlearning framework for LLMs

Identifier:  imarina:9463649

Handle: https://hdl.handle.net/20.500.11797/imarina9463649

Authors:  Al Mahmud, T; Jebreel, N; Domingo-Ferrer, J; Sánchez, D

Abstract:
Large language models (LLMs) have recently revolutionized language processing tasks but have also brought ethical and legal issues. LLMs have a tendency to memorize potentially private or copyrighted information present in the training data, which might then be delivered to end users at inference time. When this happens, a naive solution is to retrain the model from scratch after excluding the undesired data. Although this guarantees that the target data have been forgotten, it is also prohibitively expensive for LLMs. Approximate unlearning offers a more efficient alternative, as it consists of expost modifications of the trained model itself to prevent undesirable results, but it lacks forgetting guarantees because it relies solely on empirical evidence. In this work, we present DP2Unlearning, a novel LLM unlearning framework that offers formal forgetting guarantees at a significantly lower cost than retraining from scratch on the data to be retained. DP2Unlearning involves training LLMs on textual data protected using epsilon-differential privacy (DP), which later enables efficient unlearning with the guarantees against disclosure associated with the chosen epsilon. Our experiments demonstrate that DP2Unlearning achieves similar model performance post-unlearning, compared to an LLM retraining from scratch on retained data-the gold standard exact unlearning-but at approximately half the unlearning cost. In addition, with a reasonable computational cost, it outperforms approximate unlearning methods at both preserving the utility of the model post-unlearning and effectively forgetting the targeted information. The code of our experiments is available at https://github.com/tamimalmahmud/LLM-Unlearning/tree/main/ DP2Unlearning.