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Can LLMs Keep a Secret? Testing Privacy Implications of Language Models via Contextual Integrity Theory
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Introduces ConfAIde, a four-tier benchmark grounded in contextual integrity theory that tests whether instruction-tuned LLMs reason about privacy-appropriate information flow, finding that even GPT-4 and ChatGPT leak secrets in interactive settings.
Problem
LLMs receiving information from multiple sources at inference time may expose sensitive input data in inappropriate contexts; existing privacy work focuses on training-data leakage rather than contextual information flow.
Approach
Grounds privacy evaluation in contextual integrity theory with four escalating tiers (information sensitivity out of context, information-flow expectations in context, theory-of-mind secret keeping, and meeting summarization/action-item leakage), measuring inference-time privacy leakage rather than memorization.
Key results
- GPT-4 and ChatGPT reveal secrets 22% and 93% of the time in Tier 3 (string-match leakage, worst case over prompts with privacy instructions).
- Correlation with human judgment drops for GPT-4 from 0.86 in Tier 1 to 0.10 in Tier 3.
- In Tier 4 meeting tasks, GPT-4 has 0.89 error rate for action items (leaks secret or omits public info) and chain-of-thought prompting makes leakage worse rather than better.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Increase contextual complexity from Tier 1 to Tier 3 | GPT-4 judgments on ConfAIde · ConfAIde Tier 1 to Tier 3 | Pearson correlation with human judgments: 0.86 -> 0.10 | Hurt |
| Increase contextual complexity from Tier 1 to Tier 3 | ChatGPT judgments on ConfAIde · ConfAIde Tier 1 to Tier 3 | Pearson correlation with human judgments: 0.92 -> 0.05 | Hurt |
| Use free-form privacy reasoning rather than the Tier 3 control question | GPT-4 · ConfAIde Tier 3 | Leakage thru. String Match: 0.06 -> 0.22 | Hurt |
| Add chain-of-thought prompt (ablation) | GPT-4 · ConfAIde Tier 3 | Leakage thru. String Match: 0.22 -> 0.24 | Hurt |
| Add chain-of-thought prompt (ablation) | ChatGPT · ConfAIde Tier 3 | Leakage thru. String Match: 0.93 -> 0.95 | Hurt |
| Add chain-of-thought prompt (ablation) | GPT-4 · ConfAIde Tier 4 meeting summary | Leaks Secret or Omits Info.: 0.42 -> 0.52 | Hurt |
| Add chain-of-thought prompt (ablation) | ChatGPT · ConfAIde Tier 4 meeting summary | Leaks Secret or Omits Info.: 0.74 -> 0.83 | Hurt |
| Use meeting summary generation rather than personal action-item generation | GPT-4 · ConfAIde Tier 4 | Leaks Secret: 0.29 -> 0.39 | Hurt |
| Use meeting summary generation rather than personal action-item generation | ChatGPT · ConfAIde Tier 4 | Leaks Secret: 0.38 -> 0.57 | Hurt |
| Remove privacy-preserving instructions (ablation) | GPT-4 · ConfAIde Tier 4 action items | Leaks Secret: 0.29 -> 0.38 | Hurt |
| Remove privacy-preserving instructions (ablation) | GPT-4 · ConfAIde Tier 4 meeting summary | Leaks Secret: 0.39 -> 0.68 | Hurt |
| Remove privacy-preserving instructions (ablation) | ChatGPT · ConfAIde Tier 4 meeting summary | Leaks Secret: 0.57 -> 0.66 | Hurt |
Surprising findings
- Chain-of-thought prompting ('Take a deep breath...') does not reduce leakage and often increases it.
- Removing explicit privacy-preserving instructions increases leakage, and models that are RLHF-tuned still leak secrets despite explicit instructions.
Limitations
- Tier 3 and Tier 4 scenarios are GPT-4 generated and may be familiar to GPT-4; some were filtered by annotators for safety and coherence.
- Leakage detection via exact string match may underestimate leakage; manual review found 16 missed leaks among 200 GPT-4 responses.
- Authors explicitly do not make normative judgments on what should be private, and human annotations have low inter-annotator agreement (Krippendorff's alpha 0.07-0.34).
Experimental setup
Datasets: Pew privacy study information types Martin & Nissenbaum vignette survey templates
Benchmarks: ConfAIde
Metrics: Pearson correlation with human judgments leakage rate (string match) leakage rate (proxy model) theory-of-mind error rate binary control question error rate omits public information rate
Baselines: ChatGPT InstructGPT Mixtral Llama-2 Chat Llama-2 Davinci
Builds on: contextual integrity factorial vignette survey (Martin & Nissenbaum) chain-of-thought prompting
Closest papers by meaning
- Position: Contextual Integrity is Inadequately Applied to Language Models (ICML 2025 · similarity 0.93)
- Beyond Memorization: Violating Privacy via Inference with Large Language Models (ICLR 2024 · similarity 0.92)
- Privacy Auditing of Large Language Models (ICLR 2025 · similarity 0.90)
- Contextual Integrity in LLMs via Reasoning and Reinforcement Learning (NeurIPS 2025 · similarity 0.90)
- Open LLMs are Necessary for Current Private Adaptations and Outperform their Closed Alternatives (NeurIPS 2024 · similarity 0.90)
- Privacy Reasoning in Ambiguous Contexts (NeurIPS 2025 · similarity 0.90)
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