C# Triple-Des incorrect length

Question

I am trying to make an encrypt/decrypt code for 3DES using C# built in 3Des. I am configuring it like this:

    this.tDes = new TripleDESCryptoServiceProvider ();
    this.tDes.Key = new byte[]{97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112};
    this.tDes.IV = new byte[8];
    this.tDes.Mode = CipherMode.CBC;

And this is my decript function:

    public string Decrypt(string CipherText)
    {
        byte[] cipherData = System.Text.Encoding.UTF8.GetBytes(CipherText);
        MemoryStream ms = new MemoryStream();
        CryptoStream cs = new CryptoStream(ms, this.tDes.CreateDecryptor(), CryptoStreamMode.Write);
        cs.Write(cipherData, 0, cipherData.Length);
        cs.FlushFinalBlock();
        byte[] ClearBytes = ms.ToArray();
        ms.Close();
        cs.Close();
        string decriptedData = Convert.ToBase64String(ClearBytes);
        return decriptedData;
    }

This is my encrypt function:

public string Encrypt(string InputText)
{
    byte[] clearData = System.Text.Encoding.UTF8.GetBytes(InputText);
    MemoryStream ms = new MemoryStream();
    CryptoStream cs = new CryptoStream(ms, this.tDes.CreateEncryptor(), CryptoStreamMode.Write);
    cs.Write(clearData, 0, clearData.Length);
    cs.FlushFinalBlock();
    byte[] CipherBytes = ms.ToArray();
    ms.Close();
    cs.Close();
string EncryptedData = Convert.ToBase64String(CipherBytes);
    return EncryptedData;
}

But when trying to decrypt it, C# throws an error in the line "cs.FlushFinalBlock();" saying incorrect length. What should be the correct size? What is the problem?

Answer 1

You need to decode the base 64 before decrypting it (so assign it to cipherData). Then clearBytes should be decoded using UTF8 and assigned to decriptedData.