# Oversight Registration Predicate v1

**Predicate Type URI:**

`https://github.com/oversight-protocol/oversight/blob/v0.5.0/docs/predicates/registration-v1.md`

**Statement type:** `https://in-toto.io/Statement/v1`

**Envelope:** DSSE (`application/vnd.in-toto+json`)

**Signature algorithm:** Ed25519 (issuer key from the Oversight manifest)

## Purpose

This predicate describes the act of an Oversight issuer registering a sealed

file's mark with a public transparency log (Sigstore Rekor v2). The DSSE

envelope is uploaded to Rekor; the returned `TransparencyLogEntry` is then

embedded in the local evidence bundle.

The predicate is intentionally minimal on the public log - recipient

identifiers and pubkeys are hashed before publication so the log cannot be

mined for "who got what."

## Subject

A statement carries exactly one subject:

```json

{

  "name": "mark:<mark_id_hex>",

  "digest": {"sha256": "<plaintext sha256 hex>"}

}

```

`mark_id_hex` is the 128-bit watermark identifier in lowercase hex. It is an

opaque random value; it is NOT a human-meaningful label and contains no PII.

`digest.sha256` is the SHA-256 of the plaintext that was sealed. This is the

hook auditors use to find matching registrations when investigating a leak:

hash the leaked text, query Rekor by digest.

## Predicate body fields

| field                       | type        | required | notes                                                      |

|-----------------------------|-------------|----------|------------------------------------------------------------|

| `predicate_version`         | int         | yes      | Always `1` for this URI.                                   |

| `file_id`                   | string UUID | yes      | The Oversight manifest's `file_id`.                        |

| `issuer_pubkey_ed25519`     | hex string  | yes      | Verifying key for the DSSE envelope and the manifest.      |

| `recipient_id`              | string      | yes      | SHOULD be a hash or UUID. Issuers MUST NOT publish raw PII.|

| `recipient_pubkey_sha256`   | hex string  | yes      | `sha256(recipient_x25519_pub_raw_bytes)`. NEVER the raw key.|

| `suite`                     | string      | yes      | `OSGT-CLASSIC-v1` / `OSGT-PQ-HYBRID-v1` / `OSGT-HW-P256-v1`.|

| `registered_at`             | string      | yes      | ISO 8601 UTC timestamp.                                    |

| `policy`                    | object      | yes      | Subset of the manifest policy that bears on attribution.   |

| `watermarks`                | object      | yes      | `{L1:bool, L2:bool, L3:bool}` - which layers were embedded.|

| `rfc3161_tsa`               | string URL  | optional | TSA endpoint used.                                         |

| `rfc3161_token_b64`         | base64      | optional | Raw RFC 3161 TimeStampToken.                               |

| `rfc3161_chain_b64`         | base64      | optional | Concatenated PEM cert chain for TSA validation post-expiry.|

## Privacy contract

The on-log payload MUST NOT contain:

- Raw recipient public keys.

- Email addresses, phone numbers, or other directly identifying recipient PII.

- File content, even ciphertext.

- Watermark mark_ids belonging to other recipients of the same source file

  (one statement, one recipient).

Issuers who need to retain the raw recipient pubkey MUST keep it in the local

`.sealed` bundle, not in the DSSE envelope.

## Versioning

Backward-incompatible changes to this predicate body produce a new file at a

new git tag, e.g. `…/blob/v0.6.0/docs/predicates/registration-v2.md`. The URI

itself is the version anchor; never re-edit a published predicate URI's

contents.