# HXP-002 — Physical Token Envelope and Carrier

Status: Candidate Standard 0.1
Protocol: `helix-token/1.0`

## Carrier profile

The baseline carrier is an NFC Forum Type 4 tag with 8 KiB EEPROM integrated into a segmented frangible antenna. The NDEF payload budget is 7,680 bytes; implementations must fail instead of truncating. QR or Data Matrix contains only a certificate locator and NFC-required marker.

## Envelope

The deterministic-CBOR envelope contains a signed payload and an issuer delegation. The payload commits to the certificate, evidence root, subject digest, optical design digest, optical and attachment profiles, PUF-template digest, unit and lot identifiers, NFC profile, and commissioning time.

The payload and delegation use ML-DSA-44 with separate domains. The full `.hlx` retains its configured ML-DSA/SLH-DSA suite. This split fits a standardized offline carrier while preserving redundant signatures in the larger evidence capsule.

## Trust

The envelope includes the operational public key and its root-signed delegation. A verifier must obtain or already possess the trusted root independently. A root supplied only by the token is cryptographically self-consistent but untrusted. Revocation and newer custody events require a current registry observation.

## Write lifecycle

The unit is uncommissioned when manufactured. After optical enrollment and attachment, Helix writes the envelope, verifies the readback and exact byte count, records the commissioning event, seals the checkpoint, appends the receipt, and write-locks the carrier. Password protection is an operational control, not the authenticity primitive.