sign method

@override Uint8List? sign(SignKey privateKey)

Signs the TAI data with the entity's private key.

Encodes all properties to a data string, signs it with the private key, and stores the signature for later verification.

sKey is the private key matching the entity's Meta public key.

Returns the signature as Uint8List if successful, null on error.

Implementation

@override
Uint8List? sign(SignKey privateKey) {
  Uint8List? signature;
  // if (_status > 0) {
  //   // already signed/verified
  //   assert(_json != null, 'document data error: $this');
  //   signature = _getSignature();
  //   assert(signature != null, 'document signature error: $this');
  //   return signature;
  // }
  // 1. update sign time
  setProperty('time', DateTime.now().millisecondsSinceEpoch / 1000.0);
  // 2. encode & sign
  Map? dict = properties;
  if (dict == null) {
    assert(false, 'document invalid: ${toMap()}');
    return null;
  }
  String data = JSONMap.encode(dict);
  assert(data.isNotEmpty, 'should not happen: $dict');
  signature = privateKey.sign(UTF8.encode(data));
  assert(signature.isNotEmpty, 'should not happen: $dict');
  TransportableData ted = Base64Data.createWithBytes(signature);
  // 3. update 'data' & 'signature' fields
  this['data'] = data;                 // JSON string
  this['signature'] = ted.serialize();  // BASE-64
  _json = data;
  _sig = ted;
  // 4. update status
  _status = 1;
  return signature;
}