# Device to Receipt Trust Boundaries

What a signature can establish, and what remains unknown

Published September 3, 2026.

## Quick answer

A valid Ed25519 signature proves control of a signing key for a specific canonical message. It does not prove that the key lived in genuine hardware. Device receipts need explicit enrollment, assignment, calibration, timing, sequence, and trust relations.

## The problem

Device evidence often jumps from a valid signature to a hardware claim. That jump is unsafe. A signature authenticates a key and message. Genuine device identity depends on how the key was enrolled, assigned, protected, and linked to a trust root.
The three profiles make uncertainty visible. Unknown trust produces an indeterminate outcome. It never becomes a favorable hardware claim by default.

## Primitive map

| Receipt | Bound inputs | Derived relation | Claim boundary |
| --- | --- | --- | --- |
| hiveseal.qpuf | Signed challenge response, nonce, observation time, enrollment, and trust class | Message and binding relations verify | Unclonability, physical origin, or quantum origin |
| ppr.wearable | Signed reading, subject assignment, calibration, sequence, and time | Reading is bound to the enrolled key and supplied relations | Subject identity, clinical validity, or diagnosis |
| s2s.signature | Device and platform messages, assignment, nonce, time, and trust root | Both signatures and trust relations verify | Genuine GPU hardware without verified trust evidence |

## Verifier gates

The verifier rebuilds derived values. It does not trust a caller supplied outcome, count, root, total, or relation.

- `DEVICE_SIGNATURE`
- `PLATFORM_SIGNATURE`
- `NONCE_BINDING`
- `TIME_RELATION`
- `SEQUENCE_RELATION`
- `ENROLLMENT_RELATION`
- `ASSIGNMENT_RELATION`
- `CALIBRATION_RELATION`
- `TRUST_CLASSIFICATION`

## Failure cases

### Message substitution

The signature fails on changed canonical bytes.
### Nonce replay

The message must bind the expected challenge nonce.
### Stale observation

Freshness and ordering relations are recomputed.
### Sequence rollback

A lower or repeated sequence fails the declared relation.
### Unknown trust

The outcome remains indeterminate instead of asserting genuine hardware.

## Claim boundary

- A key signature is not proof of physical device identity.
- QPUF evidence does not prove unclonability or quantum origin.
- Wearable evidence does not identify the human subject or establish clinical validity.
- S2S evidence does not claim genuine vendor hardware without a verified trust root.

## Standards context

- [W3C Verifiable Credentials 2.0](https://www.w3.org/TR/vc-data-model-2.0/)
- [RFC 9396](https://www.rfc-editor.org/rfc/rfc9396.pdf)
- [Model Context Protocol authorization](https://modelcontextprotocol.io/specification/2025-11-25/basic/authorization)

## Related research

- [Swarm incident receipt autopsy](https://thehiveryiq.com/autopsy/openai-hugging-face-agent-evaluation/)
- [Hive research index](https://thehiveryiq.com/papers/)