private async Task <List <string> > GetOutOfSyncAddressesAsync()
        {
            var qbitResult = await _qBitNinjaWalletClient.GetAddresses();

            var qbitAddresses = qbitResult.Select(x => x.Address.ToString()).ToList();
            var safeAddresses = new HashSet <string>();

            for (var i = 0; i < AddressCount; i++)
            {
                safeAddresses.Add(KeyRing.GetAddress(i));
            }

            if (qbitAddresses.Any(qbitAddress => !safeAddresses.Contains(qbitAddress)))
            {
                throw new Exception("QBitNinja wallet and HTTPKeyRingMonitor is out of sync.");
            }

            return(safeAddresses.Where(safeAddress => !qbitAddresses.Contains(safeAddress)).ToList());
        }