payloadHashSignature

[arkavo-com]

Proposed Changes

• Add payload.hash to manifest for easy, external usage
• Add PKI signature capability to TDF (instead of wrappedKey signature)
• Unencrypted payload integrity check without a KAS call
• JsonWebKey2020 and PEM example for payloadHashSignature.sigKey
• Not addressed here:
  • Protocol to do signing
  • Manifest signing

Alternatives

• Use assertions perhaps

Checklist

• A clear description of the change has been included in this PR.
• A clear description of whether this change is a Major, Minor, Patch or cosmetic change as per the Versioning Guidelines has been included in this PR.
• All schema validation tests have been updated appropriately and are passing.
• MAJOR/MINOR VERSION CHANGES ONLY: This PR should be made in branches prefixed with draft-<change>
• MAJOR/MINOR VERSION CHANGES ONLY: A link to a reference implementation (PR or set of PRs) of the change has been included in this PR.
• MAJOR/MINOR VERSION CHANGES ONLY: A writeup has been included discussing the motivation and impact of this change.
• MAJOR/MINOR VERSION CHANGES ONLY: The minimum wait time has elapsed.
• DRAFT MERGE ONLY: Draft Semver has been updated in the VERSION file (optional)
• DRAFT MERGE ONLY: Tagged this branch with new semver version and an annotation describing the change (ex: git tag -s 4.1.0 -m "Spec version 4.1.0 - did a thing")
• DRAFT MERGE ONLY: Version numbers have been updated as per the Versioning Guidelines.
• This change otherwise adheres to the project Contribution Guidelines.