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Allow Credentials to Be Associated with Softbinding Entries #72
Description
In regards to #61
Different watermarking technologies provide different levels of utility, robustness, resilience, and assurance. However, C2PA should not be responsible for benchmarking or ranking individual watermarking technologies.
Performing this evaluation within C2PA would require defining test methodologies, thresholds, environmental assumptions, and potentially maintaining comparative assessments as watermarking technologies evolve.
Instead, the softbinding registry should allow an entry to reference an external credential or certification associated with the watermark.
Proposal
Allow a softbinding entry to optionally include one or more credentials.
Each credential reference should include, at minimum:
Credential URL — A link to the credential, certification, attestation, or other machine-readable evidence.
Credential type — The type of credential or certification being referenced.
For example:
{
"credentials": [
{
"type": "example.watermark.robustness-certification",
"url": "https://example.org/credentials/12345"
}
]
}
This would allow independent organizations, certification bodies, industry groups, or other authorities to make claims about the characteristics of a watermark without requiring C2PA itself to evaluate those claims.
Those credentials could include values for robustnessEvidence or other metadata.
Rationale
C2PA's role should be to provide the mechanism for identifying and using softbindings, rather than determining whether one watermark is more robust or useful than another.
Associating credentials with a softbinding entry would allow external schemes to attest to properties such as robustness, interoperability, conformance, or suitability for a particular use case while keeping those assessments outside of the C2PA specification.
The presence of a credential should not imply endorsement by C2PA; it simply provides a discoverable reference to an external assertion about the softbinding technology.
Activity
titusz commentedon Sep 30, 2026
I support this proposal. A credential field keeps C2PA out of benchmarking and ranking. It still lets implementers select entries on properties they can check.
For interoperability, the key property is whether a validator can compute the binding, verify it, and test its own implementation. I propose the following three credential types:
open-source-implementation: a public repository under an OSI-approved license that generates and matches the binding. A few entries already link to such repositories.conformance-test-vectors: published inputs with expected outputs. An independent implementation can show that it gets the same results.international-standard: the catalogue entry of a published standard from a recognized standards body. The algorithm is under formal change control.These types say nothing about robustness. Any entry qualifies once its owner publishes the material. The link checker from #77 can test the URLs.
Disclosure: I chair the ISCC Foundation. Entry 3 (io.iscc.v0) would qualify for all three types.
jcollomosse commentedon Sep 30, 2026
Via informationalUrl, there already exists a way to provide information on the soft binding algorithm, which could also include benchmarking information.
It might also be beneficial to allow linking out explicitly to benchmarking information via introducing another 'benchmark information URL' field, appropriately named.
I think that including specific quantitative data on benchmarks would be nearly meaningless. For watermarking, for example, generally speaking, people benchmark on quality and robustness. Metrics for these are well defined, but experimental setups for them are not. Robustness can mean almost anything, depending on the transformations content undergoes and that in turn depends on the use case. Further, quality is often traded against robustness.
Including numbers is therefore meaningless without context, and providing that context and a strong enough ontology around is it highly complex and takes us far from our goals of ensuring watermark interoperability for C2PA.
domguinard commentedon Sep 30, 2026
Hi all, note that this is now being addressed in PR: #79
and the corresponding issue in the CORE repo: https://github.com/c2pa-org/specs-core/issues/2540