Question

I use the following code to encrypt a string with a key, using the 3-DES algorithm:

private bool Encode(string input, out string output, byte[] k, bool isDOS7)
    {
        try
        {
            if (k.Length != 16)
            {
                throw new Exception("Wrong key size exception");
            }
            int length = input.Length % 8;
            if (length != 0)
            {
                length = 8 - length;
                for (int i = 0; i < length; i++)
                {
                    input += " ";

                }
            }
            TripleDESCryptoServiceProvider des = new TripleDESCryptoServiceProvider();

            des.Mode = CipherMode.ECB;
            des.Padding = PaddingMode.Zeros;
            des.Key = k;
            ICryptoTransform ic = des.CreateEncryptor();



            byte[] bytePlainText = Encoding.Default.GetBytes(input);
            MemoryStream ms = new MemoryStream();
            CryptoStream cStream = new CryptoStream(ms,
                ic,
                CryptoStreamMode.Write);

            cStream.Write(bytePlainText, 0, bytePlainText.Length);
            cStream.FlushFinalBlock();
            byte[] cipherTextBytes = ms.ToArray();
            cStream.Close();
            ms.Close();
            output = Encoding.Default.GetString(cipherTextBytes);

        }
        catch (ArgumentException e)
        {
            output = e.Message;
            //Log.Instance.WriteToEvent("Problem encoding, terminalID= "+objTerminalSecurity.TerminalID+" ,Error" + output, "Security", EventLogEntryType.Error);
            return false;
        }
        return true;
    }

I send the output parameter as is over to a WCF http-binding webservice, and I noticed that the actual encoded string looks different, it looks like there are some \t and \n but the charachters are about the same.

What is going on, why does the server get a different encoded string?

Answer 1

Usually cipher text is base64 encoded in an effort to be binary safe during transmission.

Also I would not use 3DES with ECB. That is awful, you must have copy pasted this from somewhere. Use AES with cbc mode and think about adding a cmac or hmac.