Proof Set and Chain Test Vectors

[Wind4Greg]

This PR provides test vectors (informational) for proof sets and chains for the eddsa-rdfc-2022 based on the updated procedures in the VC Data Integrity specification.

• Starting with a document with a single proof add a proof to form a simple proof set.
• Starting with a document with a proof set, add a proof to form a proof chain. In this case we will also demonstrate where previousProof can be any array, i.e., the new proof relies on two other proofs.
• Starting with a document with a proof chain, add a proof to form a longer proof chain.

These test vectors make use of the same starting unsigned document used for all previous test vectors and adds a collection of four public/private key pairs for use in generating the test vectors.

---

Preview | Diff

[dlongley]

I haven't run this through an implementation yet, but it looks good from reading over it. Getting multiple implementations to confirm against the test suite will be the next step. Thanks!

[dlongley]

IIRC, these should all be secretKeyMultibase:

Suggested change

	"privateKeyMultibase": "z3u2W4YnTstS1nSSBAgZcYSJF43JuZ9uLV6bF38B1Bf8NugW"
	"secretKeyMultibase": "z3u2W4YnTstS1nSSBAgZcYSJF43JuZ9uLV6bF38B1Bf8NugW"

[Wind4Greg]

Did a quick survey. Wikipedia (https://en.wikipedia.org/wiki/Public-key_cryptography) for public key cryptography uses the terms public and private key. Multi-codecs uses the terms public and private for the different parts of a key pair. Boneh and Shoup (https://crypto.stanford.edu/~dabo/cryptobook/BonehShoup_0_6.pdf) use the terms public and secret key. But I think that's so they can use terse notation such as sk and pk. All the test vectors in this document use the public/private terminology. Since both are common in the literature this should not cause confusion and I'd prefer not to change all the test vectors.

[msporny]

The Data Integrity specifications use the term secretKeyMultibase, as defined here: https://w3c.github.io/vc-data-integrity/#multikey

[dlongley]

Hard to tell from the diff here if this is already in a section marked "non-normative", but if not, we need to add that.

[Wind4Greg]

The entire test vector section is marked as informative:

    <section class="appendix informative">
      <h2>Test Vectors</h2>
      <section>
        <h3>Representation: eddsa-rdfc-2022</h3>

[msporny]

Editorial, multiple reviews, changes requested and made, no objections, merging.