buildProof method

@override Future<Map<String, dynamic>> buildProof(dynamic data, WalletStore wallet, String did, { String? challenge, String? domain, String? proofPurpose, })

Build a LinkedDataProof / DataIntegrityProof

Implementation

@override
Future<Map<String, dynamic>> buildProof(data, WalletStore wallet, String did,
    {String? challenge, String? domain, String? proofPurpose}) async {
  var proofOptions = {
    '@context': ecdsaRecoveryContextIri,
    'type': typeName,
    'proofPurpose': proofPurpose ?? 'assertionMethod',
    'verificationMethod': '$did#controller',
    'created': DateTime.now().toUtc().toIso8601String()
  };
  if (domain != null) {
    proofOptions['domain'] = domain;
  }
  if (challenge != null) {
    proofOptions['challenge'] = challenge;
  }

  List<int> hash = await _dataToHash(data);

  var pOptionsHash = sha256
      .convert(utf8.encode(await JsonLdProcessor.normalize(proofOptions,
          options:
              JsonLdOptions(safeMode: true, documentLoader: loadDocument))))
      .bytes;
  var payload = pOptionsHash + hash;

  var critical = <String, dynamic>{};
  critical['b64'] = false;
  var header = buildJwsHeader(alg: 'ES256K-R', extra: critical);
  var headerEnc = removePaddingFromBase64(header);

  var hashToSign = sha256.convert(utf8.encode('$headerEnc.') + payload).bytes;

  //proofOptions.remove('@context');

  var privateKeyHex = await wallet.getPrivateKeyForCredentialDid(did);
  privateKeyHex ??= await wallet.getPrivateKeyForConnectionDid(did);
  if (privateKeyHex == null) throw Exception('Could not find a private key');
  var key = EthPrivateKey.fromHex(privateKeyHex);

  var sigArray = _buildSignatureArray(Uint8List.fromList(hashToSign), key);
  while (sigArray.length != 65) {
    sigArray = _buildSignatureArray(Uint8List.fromList(hashToSign), key);
  }

  proofOptions['jws'] = '$headerEnc.'
      '.${base64UrlEncode(sigArray)}';

  return proofOptions;
}