Ingredients

Overview

Digital assets are often not created entirely from scratch, but instead created from one or more existing assets, for example placing an image into a layer in Photoshop. Such constituent assets are called ingredients.

This documentation covers C2PA v1 ingredients. The C2PA Technical Specification also describes improved v2 ingredients.

note

The C2PA Technical Specification describes ingredient assertions but the CAI SDK treats ingredients separately as their own objects in the JSON manifest rather than as a type of assertion.

Ingredient objects

Each ingredient used to create an asset is listed in the JSON manifest ingredients array. When an ingredient itself has Content Credentials, those manifests are included in the composed asset's manifest store to keep the provenance data intact.

The ingredients array contains an ingredient object for each ingredient. The only required property of the ingredient object is the title property, which usually is the source file name.

Other important properties of the ingredient object include:

format: MIME type of the source file.
document_id and instance_id which are derived from the ingredient asset's XMP metadata.
thumbnail: Object with properties that identify the thumbnail image.
active_manifest: For an ingredient with a manifest store, the label of the active manifest.
relationship: One of parentOf, componentOf, or inputTo. See Relationship below.

For example:

     "ingredients": [
        ...
      {
        "title": "CAI.jpg",
        "format": "image/jpeg",
        "instance_id": "xmp:iid:315e20bf-10da-4f44-85f4-6de350bfe688",
        "thumbnail": {
          "format": "image/jpeg",
          "identifier": "xmp-iid-315e20bf-10da-4f44-85f4-6de350bfe688.jpg"
        },
        "relationship": "componentOf",
        "active_manifest": "contentauth:urn:uuid:8bb8ad50-ef2f-4f75-b709-a0e302d58019"
      }
    ]

Relationship

The ingredient object's relationship property describes its relationship to the current asset. This property can have one of three values, as described in the table below.

Value of `relationship`	Description
`parentOf`	The current asset is a derived asset or asset rendition of this ingredient. This relationship value is also used with update manifests. There can be at most one parent ingredient in a manifest.
`componentOf`	This ingredient is one of the assets that composes the current asset.
`inputTo`	This ingredient was used as input to a computational process, such as an AI/ML model, that led to the creation or modification of this asset.

Validation status

When ingredients are added, the SDK validates their Content Credentials (if any). However, the validation status of an ingredient does not imply anything about the validation status of the composed asset containing the ingredient. In other words:

A composed asset's Content Credentials may be valid, but one or more of its ingredients may have invalid Content Credentials. For example, test file adobe-20220124-XCA.jpg
A composed asset's Content Credentials may be invalid, but one or more of its ingredients may have valid Content Credentials. For example, test file adobe-20220124-CIE-sig-CA.jpg.

note

Ingredient certificates are validated when they are added to the manifest store, NOT during validation of the composed asset.

Example of ingredient with invalid credentials

As noted above, the test file adobe-20220124-CIE-sig-CA.jpg has an ingredient with invalid Content Credentials, as shown in this snippet from the manifest store:

...
{
  "active_manifest": "contentauth:urn:uuid:40f2636a-402c-4792-9da4-644a63d1f7d0",
  "manifests": {
    "contentauth:urn:uuid:40f2636a-402c-4792-9da4-644a63d1f7d0": {
    ...
    "ingredients": [
      {
        "title": "E-sig-CA.jpg",
        "format": "image/jpeg",
        "instance_id": "xmp:iid:81ca15f6-4ed0-422a-96cb-3e8014e29ac6",
        "thumbnail": {
          "format": "image/jpeg",
          "identifier": "xmp-iid-81ca15f6-4ed0-422a-96cb-3e8014e29ac6.jpg"
        },
        "relationship": "componentOf",
        "active_manifest": "contentauth:urn:uuid:04cdf4ec-f713-4e47-a8d6-7af56501ce4b",
        "validation_status": [
          {
            "code": "timeStamp.mismatch",
            "url": "Cose_Sign1",
            "explanation": "timestamp message imprint did not match"
          },
          {
            "code": "claimSignature.mismatch",
            "url": "self#jumbf=/c2pa/contentauth:urn:uuid:04cdf4ec-f713-4e47-a8d6-7af56501ce4b/c2pa.signature",
            "explanation": "claim signature is not valid"
          }
          ...
        ]
      }
    ]

Examples

The C2PA public-testfiles repository has several examples of images with multiple ingredients:

Overview​

Ingredient objects​

Relationship​

Validation status​

Example of ingredient with invalid credentials​

Examples​