Nikolaos Laoutaris

INDEXGUARD: Index-only Backdoor Vetting for Secure Federated PEFT of Large Language Models

Federated parameter-efficient fine-tuning (PEFT) enables customizing large language models on private data, yet it is vulnerable to backdoor poisoning—especially when privacy constraints prevent inspection of per-client real-valued updates. We exploit the intuition that poisoning leaves a similar ba…