Eliciting Secret Knowledge from Language Models
Authors: name: Bartosz Cywiński; name: Emil Ryd; name: Rowan Wang; name: Senthooran Rajamanoharan; name: Neel Nanda; name: Arthur Conmy; name: Samuel Marks
Published: 2025-10-01 16:12:28

Abstract: We study secret elicitation: discovering knowledge that an AI possesses but
does not explicitly verbalize. As a testbed, we train three families of large
language models (LLMs) to possess specific knowledge that they apply downstream
but deny knowing when asked directly. For example, in one setting, we train an
LLM to generate replies that are consistent with knowing the user is female,
while denying this knowledge when asked directly. We then design various
black-box and white-box secret elicitation techniques and evaluate them based
on whether they can help an LLM auditor successfully guess the secret
knowledge. Many of our techniques improve on simple baselines. Our most
effective techniques (performing best in 2/3 settings) are based on prefill
attacks, a black-box technique where the LLM reveals secret knowledge when
generating a completion from a predefined prefix. In our remaining setting,
white-box techniques based on logit lens and sparse autoencoders (SAEs) are
most effective. We release our models and code, establishing a public benchmark
for evaluating secret elicitation methods.