Extension: ramp-c2pa-v1

Overview

RAMP-C2PA v1 integrates the C2PA (Coalition for Content Provenance and Authenticity) standard into RAMP, enabling agents and Exchanges to:

• Verify content provenance — who created it, what tools were used, whether it’s been modified
• Enforce creator-declared training/mining restrictions commercially via RAMP access controls
• Resolve disputes with stronger evidence using C2PA hard and soft content bindings
• Filter for provenance-verified content at discovery time

C2PA proves what content IS (provenance). RAMP manages what you can DO with it (commercial access). This profile bridges the two.

Design Principle: Consume Results, Not Structures

RAMP does not re-implement C2PA internals. C2PA has its own container format (JUMBF), its own PKI (X.509 certificates), and its own validation algorithm (COSE Sign1). This profile defines how C2PA validation results are carried in RAMP’s existing attestation mechanism — not how to parse JUMBF or verify COSE signatures.

A C2PA verification vendor (the Exchange itself, or a third party like Truepic or a C2PA Trust List validator) validates the manifest and publishes results as a standard RAMP ResourceAttestation. C2PA-unaware agents benefit from the results without needing C2PA libraries.

Who Should Implement This

• Exchanges serving content with C2PA credentials (news photos, AI-generated images, medical imaging, legal documents)
• Verification vendors that validate C2PA manifests and bridge the results into RAMP attestations
• Agents that need provenance assurance for high-stakes content (medical, legal, financial)
• Providers that embed C2PA credentials in their content and want RAMP to enforce their training/mining declarations

Prerequisites

Implementers must be familiar with:

• RAMP protocol (proto/ramp/v1/ramp.proto)
• ResourceIdentity, ResourceAttestation, and AccessRestrictions messages
• The ext field mechanism (google.protobuf.Struct)
• C2PA Specification 2.3 (recommended, not required for consumers)

---

Profile Declaration

An Exchange declares support by including "ramp-c2pa-v1" in ExchangeManifest.supported_profiles:

{
  "ver": "1.0",
  "domain": "exchange.example.com",
  "supported_profiles": ["ramp-c2pa-v1"],
  "accepted_verifiers": ["truepic.com", "contentcredentials.org"]
}

---

Core Proto Fields

These fields are in the core ramp.proto (Layer 1), not in ext:

ResourceIdentity

Field	Type	Description
c2pa_manifest	string	URI to the C2PA content credentials manifest (sidecar, embedded, or Content Credentials Cloud)
c2pa_status	C2PAStatus	Summary validation result: TRUSTED, VALID, INVALID, or ABSENT
soft_binding	string	Content-derived identifier surviving format transcoding (from C2PA soft binding assertion)
soft_binding_method	string	Algorithm: "phash-v1", "c2pa-watermark", "chromaprint"

C2PAStatus Enum

Value	C2PA Equivalent	Meaning
TRUSTED	Well-formed + valid + trusted	Signature verifies AND signer chains to C2PA Trust List
VALID	Well-formed + valid	Signature verifies, but signer not in C2PA Trust List
INVALID	Validation failed	Signature mismatch, malformed manifest, or broken binding
ABSENT	No manifest	Content was checked — no C2PA credentials present

---

Attestation Claims Vocabulary

When a C2PA verification vendor validates a manifest, it publishes results as a RAMP ResourceAttestation with these standardized claim names:

Identity & Trust Claims

Claim Key	Type	Description
c2pa.status	string	"trusted", "valid", "invalid" — mirrors C2PAStatus enum
c2pa.signer	string	X.509 subject common name from the signing certificate
c2pa.signer_org	string	Organization from the signing certificate
c2pa.signer_domain	string	Domain extracted from the signer’s certificate (SAN or CN)
c2pa.trust_list	string	URI of the trust list used for validation (e.g., "c2pa.org/trust-list-v2")
c2pa.signed_at	string	ISO 8601 timestamp from the claim signature
c2pa.tsa	string	Time Stamping Authority domain (if RFC 3161 timestamp present)
c2pa.tsa_time	string	ISO 8601 authenticated time from TSA (stronger than signed_at)

Provenance Claims

Claim Key	Type	Description
c2pa.actions	string[]	Summary of c2pa.actions.v2 history. Values: "c2pa.created", "c2pa.edited", "c2pa.color_adjusted", "c2pa.cropped", "c2pa.redacted", "c2pa.watermarked", etc.
c2pa.source_type	string	"human", "ai", "hybrid" — from C2PA sourcetype (0, 1, 2)
c2pa.claim_generator	string	Software that generated the manifest (e.g., "Adobe Photoshop 26.0")
c2pa.ingredients_count	integer	Number of c2pa.ingredient.v3 assertions (composition depth)

Rights & Mining Claims

Claim Key	Type	Description
c2pa.training_allowed	boolean	From c2pa.training_mining assertion — whether content may be used for AI/ML training
c2pa.mining_allowed	boolean	From c2pa.training_mining assertion — whether content may be data-mined

Content Binding Claims

Claim Key	Type	Description
c2pa.hard_binding_alg	string	Hard binding algorithm: "sha256", "sha384", "sha512"
c2pa.hard_binding_valid	boolean	Whether the hard binding hash matches current content
c2pa.soft_binding_alg	string	Soft binding algorithm (if present): "phash-v1", watermark ID
c2pa.soft_binding_hash	string	Soft binding value (copied to ResourceIdentity.soft_binding)

Example: Bridged C2PA Attestation

{
  "verifier": "truepic.com",
  "kid": "truepic-2026-Q1",
  "attested_at": "2026-03-20T14:00:00Z",
  "uri": "https://reuters.com/photos/2026/03/20/climate-summit.jpg",
  "claims": {
    "c2pa.status": "trusted",
    "c2pa.signer": "Reuters News & Media Inc.",
    "c2pa.signer_domain": "reuters.com",
    "c2pa.trust_list": "c2pa.org/trust-list-v2",
    "c2pa.signed_at": "2026-03-20T11:30:00Z",
    "c2pa.tsa": "digicert.com",
    "c2pa.actions": ["c2pa.created", "c2pa.color_adjusted"],
    "c2pa.source_type": "human",
    "c2pa.claim_generator": "Reuters IPTC Photo Desk 4.1",
    "c2pa.ingredients_count": 0,
    "c2pa.training_allowed": false,
    "c2pa.mining_allowed": false,
    "c2pa.hard_binding_alg": "sha256",
    "c2pa.hard_binding_valid": true,
    "content_hash": "sha256:a1b2c3d4e5f6...",
    "hash_method": "sha256"
  },
  "signature": "base64-encoded-ed25519-signature"
}

---

Rights Enforcement Mapping

The Exchange SHOULD automatically map C2PA training/mining declarations to RAMP access restrictions:

C2PA Assertion	RAMP Mapping
c2pa.training_mining.training_allowed == false	AccessRestrictions.prohibited_functions += "ai_train"
c2pa.training_mining.mining_allowed == false	AccessRestrictions.prohibited_functions += "ai_index"
c2pa.training_mining absent	No restriction inferred (absence is not prohibition)

This creates a two-layer enforcement model:

1. Declaration layer (C2PA): The content creator embeds their intent in the content itself. This travels with the content, even outside RAMP channels.
2. Enforcement layer (RAMP): The Exchange reads the C2PA declaration and enforces it commercially — an agent requesting intended_use: "ai_train" will not receive offers for content where training is prohibited.

---

Dispute Enhancement

C2PA content bindings strengthen RAMP’s dispute resolution:

Hard Binding Disputes

When an agent files DISPUTE_REASON_CONTENT_MISMATCH and the offer carried c2pa_status: TRUSTED, the Exchange can:

1. Re-validate the C2PA hard binding against the received_content_hash in the dispute
2. If the C2PA hard binding was sha256 and the agent’s received hash matches the C2PA hash but differs from the offer’s content_hash — the provider modified the content after attestation (provider fault)
3. Auto-resolve as RESOLUTION_TYPE_CREDIT

Soft Binding Disputes

When content is legitimately transcoded (image resized, PDF extracted to text) and the hard hash no longer matches:

1. The agent computes a soft binding hash from received content using soft_binding_method
2. Compares against ResourceIdentity.soft_binding
3. If the soft binding matches, the content is substantively the same despite format change — dispute SHOULD be rejected
4. If the soft binding also mismatches, this is genuine content substitution — dispute SHOULD be upheld

---

Trust Bridging

C2PA and RAMP use different PKI:

Aspect	C2PA	RAMP
Key format	X.509 certificates	Ed25519 JWKS
Trust model	Centrally curated Trust Lists (CA hierarchy)	Decentralized (provider ↔ exchange manifests)
Signature format	COSE Sign1 (RFC 9052)	JWS Compact (RFC 7515)
Timestamping	RFC 3161 TSA (cryptographic proof)	Self-declared attested_at

The verification vendor bridges these worlds:

C2PA World                          RAMP World
─────────────────                   ──────────────────
X.509 cert chain                    Ed25519 JWKS
COSE Sign1 signature    ──►        JWS EdDSA signature
C2PA Trust List          Vendor     RAMP accepted_verifiers
JUMBF manifest          bridges     ResourceAttestation.claims
RFC 3161 TSA                        attested_at timestamp

The vendor’s Ed25519 key (published at /.well-known/ramp-verifier.json) attests to the results of X.509/COSE validation. RAMP participants trust the vendor; the vendor trusts the C2PA Trust List. One-way bridge, clean separation.

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Conformance Levels

Minimum Viable (Level A)

• Populate ResourceIdentity.c2pa_manifest when content has C2PA credentials
• Populate c2pa_status with validation result
• Declare "ramp-c2pa-v1" in ExchangeManifest.supported_profiles

Standard (Level B)

All of Level A, plus:

• Publish a C2PA-bridged ResourceAttestation with identity and rights claims (c2pa.status, c2pa.signer, c2pa.training_allowed, c2pa.mining_allowed)
• Map c2pa.training_mining to AccessRestrictions.prohibited_functions
• Extract content_hash from C2PA hard binding into attestation claims

Full (Level C)

All of Level B, plus:

• Include provenance claims (c2pa.actions, c2pa.source_type, c2pa.ingredients_count)
• Extract and populate soft_binding / soft_binding_method from C2PA soft binding assertions
• Use soft binding evidence in dispute resolution
• Support TSA-grade temporal claims (c2pa.tsa, c2pa.tsa_time)

---

Crypto Stack Compatibility

Both C2PA and RAMP support Ed25519/EdDSA. A verification vendor that holds both an X.509 certificate (for C2PA signing) and an Ed25519 key (for RAMP attestation signing) can participate in both ecosystems.

Algorithm	C2PA Support	RAMP Support
Ed25519	Yes (EdDSA via COSE)	Yes (EdDSA via JWS)
ECDSA P-256	Yes	No
RSA	Yes	No
SHA-256	Yes (hard binding)	Yes (content_hash)
SHA-384/512	Yes	Yes (hash_method field)

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Relationship to Other Profiles

• ramp-news-v1: News photos with C2PA credentials benefit from both profiles. The news profile tracks editorial metadata (corrections, retractions); the C2PA profile tracks content provenance (camera, edits, creator identity). They compose — an offer can carry both news.* and c2pa.* claims.
• ramp-comp-v1: CoMP’s Video.c2pa, Image.c2pa, and Audio.c2pa fields carry C2PA manifest URIs at the media asset level. This profile operates at the RAMP resource level — the ResourceIdentity.c2pa_manifest is the canonical pointer, independent of CoMP.