public string decryptMessage(string message)
{
if (SymmKey != null)
{
EncryptionAES aes = new EncryptionAES(SymmKey);
return aes.Decrypt(message);
}
return string.Empty;
}
private void OnMessageReceivedEventHandler(MessageData messageData)
{
Dispatcher.Invoke(() =>
{
_logger.Debug($"Received message: '{messageData.UserInfo.Message}' from '{messageData.UserInfo.Username}'" +
$" Message type: '{messageData.UserInfo.MessageType}'");
if (messageData.UserInfo.MessageType == MessageType.Connect ||
messageData.UserInfo.MessageType == MessageType.Disconnect)
{
ChatTextBox.AppendText($"{messageData.UserInfo.Message}{Environment.NewLine}");
}
else if (messageData.UserInfo.MessageType == MessageType.ParameterE)
{
encryption.serverE = new BigInteger(messageData.UserInfo.Message,10);
}
else if (messageData.UserInfo.MessageType == MessageType.ParameterN)
{
encryption.serverN = new BigInteger(messageData.UserInfo.Message,10);
}
else if (messageData.UserInfo.MessageType == MessageType.CryptoMessage)
{
// encrypted symm key, receiver, encrypted message
string[] receiverUsernameAndMessage = messageData.UserInfo.Message.Split(new char[] { ',' }, 3);
if (_username == receiverUsernameAndMessage[1])
{
string decryptedSymmKey = encryptionRsa.DecryptSymmetricKey(receiverUsernameAndMessage[0],
encryption.D, encryption.N);
EncryptionAES aes = new EncryptionAES(decryptedSymmKey);
string message = aes.Decrypt(receiverUsernameAndMessage[2]);
message.TrimEnd();
ChatTextBox.AppendText($"{messageData.UserInfo.Username}: (private) {message} {Environment.NewLine}");
}
else
{
ChatTextBox.AppendText($"{messageData.UserInfo.Username}: {receiverUsernameAndMessage[2]}" +
$"{Environment.NewLine}");
}
}
else
{
ChatTextBox.AppendText(
$"{messageData.UserInfo.Username}: {messageData.UserInfo.Message}{Environment.NewLine}");
}
});
}
private string encryptMessage(string message, string receiverUsername, string senderUsername)
{
BigInteger n = 0, e = 0;
string encryptedSymmKey = "";
foreach (var user in Program.ConnectionManager.UsersList)
{
if (user.Username == receiverUsername)
{
n = user.N;
e = user.E;
break;
}
if (user.Username == senderUsername)
{
encryptedSymmKey = user.symmKey;
}
}
string decryptedSymmKey = _serverKeys.DecryptSymmetricKey(encryptedSymmKey, _serverKeys.D, _serverKeys.N);
symmKeyBytes = _serverKeys.EncryptSymmetricKey(decryptedSymmKey, e, n);
var EncryptionAES = new EncryptionAES(decryptedSymmKey);
return EncryptionAES.Encrypt(message);
}
