Limits of detection
What can an adversary achieve while remaining provably undetectable to a monitor, a test or an evaluation?
Detection-based security assumes that harmful behaviour leaves a trace which a monitor, a test or an evaluation can find. We establish where this assumption fails against learned agents. Perfectly secure steganography shows that a covert channel can be made information-theoretically indistinguishable from ordinary output at practical efficiency, and secret collusion shows that language-model agents can use such channels; together they bound what any monitoring protocol can detect. Illusory attacks extend the argument to observation-space attacks on reinforcement-learning agents, and unelicitable backdoors to the model itself: a backdoor that no pre-deployment test can trigger, even with white-box access. Where detection remains feasible, we construct the detectors and state what they guarantee.
Limits
- Perfectly Secure Steganography Using Minimum Entropy CouplingICLR 2023. Covered by Scientific American, Quanta Magazine and Bruce Schneier
- Secret Collusion among AI Agents: Multi-Agent Deception via SteganographyNeurIPS 2024
- Illusory Attacks: Information-Theoretic Detectability Matters in Adversarial AttacksICLR 2024, Spotlight
- Unelicitable Backdoors in Language Models via Cryptographic Transformer CircuitsNeurIPS 2024
- AI Models Can Provably Hide Arbitrary CapabilitiesNeurIPS 2026
- Tool Use Enables Undetectable Steganography in Multi-Agent LLM SystemsarXiv preprint, 2026
Where detection holds
- Detecting Multi-Agent Collusion Through Multi-Agent InterpretabilityarXiv preprint, 2026
- DEEDEE: Fast and Scalable Out-of-Distribution Dynamics DetectionarXiv preprint, 2025