anchor.diff:  }) async {
     return _HmacSecretKey(
       _asUint8ListZeroedToBitLength(keyData, length),
  -    _Hash.fromHash(hash).MD,
  +    _Hash.fromHash(hash),
     );
   }
   
  
positive.code:   }
  
    @override
    Future<Map<String, dynamic>> exportJsonWebKey() {
      throw _notImplemented;
    }
  
    @override
  
negative.code:     try {
        _withDataAsPointer(_keyData, (ffi.Pointer<ssl.Data> p) {
          final n = _keyData.length;
          _checkOp(ssl.HMAC_Init_ex(ctx, p, n, _hash.MD, ffi.nullptr) == 1);
        });
        await _streamToUpdate(data, ctx, ssl.HMAC_Update);
  
  