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Agent Skills Catalog

C2PA Specification and Architecture Guide

keywords plugin keywords, from plugin.json
  • c2pa
  • content-credentials
  • provenance
  • credentio
  • authenticity
  • ai-provenance
  • digital-source-type
plugin derived
C2PA Inspectorc2pa-inspector
conformance derived from plugin.json $schema
Targets Agent Plugins 1.0.0.
source derived
plugins/c2pa-inspector/skills/c2pa-inspect/references/c2pa-spec-guide.md

A plugin-level reference of c2pa-inspector. This location is not defined by Agent Plugins §6.1; the title below is this file's own H1, extracted, not composed.

A technical reference for the Coalition for Content Provenance and Authenticity (C2PA) metadata structures, JUMBF packaging, assertion taxonomy, and JSON manifest schemas.

1. C2PA Architecture Overview

C2PA defines an open technical standard that enables creators and publishers to attach cryptographically verifiable provenance to digital media.

+-------------------------------------------------------------------+
| Media Container (JPEG, PNG, MP4, WebP, AVIF)                      |
|                                                                   |
|  +-------------------------------------------------------------+  |
|  | C2PA Manifest Store (JUMBF Superbox)                        |  |
|  |                                                             |  |
|  |  +-------------------------------------------------------+  |  |
|  |  | Active Manifest                                       |  |  |
|  |  |  - Claim Generator (e.g. Adobe Photoshop, Credentio)  |  |  |
|  |  |  - Signature & Cert Chain (X.509, TSA timestamp)       |  |  |
|  |  |  - Assertions (actions, hash, ingredients, AI flags)  |  |  |
|  |  +-------------------------------------------------------+  |  |
|  |                                                             |  |
|  |  +-------------------------------------------------------+  |  |
|  |  | Ingredient Manifests (Parent / Input Assets)           |  |  |
|  |  +-------------------------------------------------------+  |  |
|  +-------------------------------------------------------------+  |
+-------------------------------------------------------------------+

2. Container Embeddings

C2PA packages manifests inside ISO/IEC 19566-5 JPEG Universal Metadata Box Format (JUMBF) structures:

  • JPEG: APP11 application markers (0xFFEB) with JUMBF superbox encapsulation (0x6A756D62).
  • PNG: Dedicated chunk types caPt (Content Authenticity Passthrough) or caPI.
  • MP4 / MOV: ISOBMFF uuid box keyed to C2PA UUID d8f03db5-4c9b-4263-8e54-11351c7b73d9, or root c2pa box.
  • WebP: RIFF container with a JUMB chunk identifier.
  • AVIF / HEIC: BMFF item references referencing the c2pa metadata item.
  • Standalone: Files with .c2pa extension containing the raw serialized manifest store.

3. Schema Variations: C2PA v1.x vs v2.x

Parsers must handle both legacy C2PA v1 schemas and modern C2PA v2 schemas resiliently:

Feature C2PA v1 Schema C2PA v2 Schema
Claim Block claim object claim.v2 or claim
Generator Info claim.claim_generator_info (object or array) Array of { name, version } objects
Certificate Info signature_info.issuer (flat string) signature_info.certificateInfo.issuer.CN
Assertions Format Key-value dictionary indexed by URI Array of { label, data } items
Action Assertion c2pa.actions c2pa.actions.v2
Validation Output validation.status array Categorized validationResults.{success, failure, informational}

4. Standard Assertions Dictionary

  • c2pa.actions / c2pa.actions.v2: Records editing history (created, edited, converted, color_adjustments, cropped).
  • c2pa.hash.data / c2pa.hash.bmff.v3: Cryptographic digest over the asset content bytes for tamper detection.
  • c2pa.ingredient: References upstream source assets, thumbnail representations, and prior manifests.
  • c2pa.training-mining: Machine learning training and data mining consent declarations.
  • c2pa.digital_source_type: Standard IPTC digital source categorization (e.g. digitalCapture, trainedAlgorithmicMedia).