Research paper · Systems and measurement study
Sealed Skills
Provider-bound encryption for LLM agent skills, and the limits of confidential context.
What it finds
- Sealing removes every non-model path to a skill at negligible cost: a 10 KB skill seals and opens in under half a millisecond.
- Once a skill is in context, most of it can be extracted: without defences, 72–75% of attack conversations disclosed at least half of a skill's rules.
- A guard instruction and a lexical output filter bring that to about 2%, but block 12.5–19% of legitimate replies, because models quote rules while using them.
- Sealing protects a skill's artifacts from copying; it does not make its content or function secret.
- Status
- Draftpreprint draft, not peer reviewed, v1.0
- Question
- Can an AI agent skill be encrypted so that only a chosen AI provider can open it, and how much of it can a user still extract through the model?
- Approach
- A design and prototype (HPKE to a provider-published key, no handshake), then 896 conversations with two open models across eight skills and 24 attacks, a sealing benchmark and a tool-use case study.
- References
- 61, among them RFC 9180 (HPKE), van Wyk et al. 2023 (encrypted prompts), Zhang et al. 2024 (prompt extraction) and the 2026 skill-stealing attacks.