// Return true if key was restored from message history.
private static bool TryToRestoreKeyFromDialog(ref Dialog dialog)
{
if (dialog.Messages.Count <= 0)
{
return(false);
}
// Find message in collection with type Message.ExchangeKey.
var exchangeMessageQuery =
(from Message m in dialog.Messages where m.Type == MessageType.KeyExchange select m);
IEnumerable <Message> messageQueryList = exchangeMessageQuery.ToList();
if (!messageQueryList.Any())
{
return(false);
}
var isSentByMe = false; // Change if find exchange message from current user.
foreach (var message in messageQueryList)
{
if (message.SenderUuid == AppUser.GetInstance().Uuid)
{
isSentByMe = true;
// But current user cannot decipher this message because it is encrypted by another user public key.
}
else
{
var privateKey = AppUser.GetInstance().PrivateKeyXml;
// Decrypt symmetric key.
var temp = message; // `message` variable is immutable.
if (DecryptMessageByAsymmetricAlgorithm(ref temp, privateKey))
{
// Load AES key.
dialog.Key = AesKey.FromJsonString(temp.Body);
}
}
}
if (dialog.Key == null)
{
return(false);
}
Logger.Info("AES key was restored from dialog with {0}.", dialog.Partner.Login);
// If message sent by current user only, there is no way to restore key.
// Otherwise if key was restored but was not send back to another user, current user have to do that.
if (!isSentByMe)
{
SendKeyExchangeMessage(dialog);
Logger.Info("AES key was sent back to the dialog with {0}.", dialog.Partner.Login);
}
return(true);
}