# Proposed did:webnext history format

## Header line

- first line of the log
- establish log format and base protocol
- place to override parameters like the hash function used
- list any relevant extensions

Examples:

["history:1", "did:webnext:1", {}]
["history:1", "did:webnext:1", {"ext": ["ML-KEM"]}]

## Data lines

- list of [version hash, version ID, timestamp, patch, proofs]
- hashes are based only on data in the log, not on the resulting document
- using multibase+multihash, but not CID
- proofs reference the version hash of the current log line in the `challenge` property
- the document does not contain any custom properties (`created`, `updated`, `versionId`, `proof`, `previousHash`)

Example:

["zQmbacL3sFb1VbmXGJVEGhKWja3AAbvLP9qbztjk4MHi8nA", 2, "2024-03-20T18:42:33Z", [{"op": "add", "path": "/alsoKnownAs", "value": ["did:web:example.com"]}], [{"type": "DataIntegrityProof", "cryptosuite": "eddsa-jcs-2022", "verificationMethod": "did:webnext:example.com:15ymutv3c5wkkrltlq6apjrcd#dnSuE8FBZjE5ua6Fx5l-4mD7A-uvx9vSj5AD3VGPR3Y", "created": "2024-03-20T18:42:33Z", "challenge": "zQmbacL3sFb1VbmXGJVEGhKWja3AAbvLP9qbztjk4MHi8nA", "proofPurpose": "authentication", "proofValue": "z46qJXR6Uxyt1EDGDhEJ2Gd7AfBmf5xuTVkq6LfuPZmsL2nhFqRi7g4mB2TmfDQ3fgkPZXt1cnWFzPGCjjLvdYvWC"}]]

## Version hash calculation

- take the version hash of the previous line as `prevHash`. for the first line, calculate `prevHash` using the base protocol as input, ie. `SHA2-256(b"did:webnext:1")`
- calculate the raw digest as `SHA2-256(JCS([prevHash, versionId, timestamp, patch]))`
- output version hash = `multibase(multihash(digest, "sha2-256"), "base58btc")`

Example:

hash input: JCS([
"zQmcPRLmBy5KwV74epZ9fvoEngjbukRphUdaZS1nxqKfM16",
2,
"2024-03-19T23:39:37Z",
[{"op": "add", "path": "/alsoKnownAs", "value": ["did:web:example.com"]}],
])
output: zQmYWPhdCeVuJnKS5Bg131bVcQiTwhbepUAPDYdq35jzTtF