How do I remove .net CryptoStream padding

When I use the following class the output is padded.

public static string EncryptString(string ClearText) {
  byte[] clearTextBytes = Encoding.UTF8.GetBytes(ClearText);
  System.Security.Cryptography.SymmetricAlgorithm rijn = SymmetricAlgorithm.Create();
  MemoryStream ms = new MemoryStream();
  byte[] rgbIV = Encoding.ASCII.GetBytes("ryojvlzmdalyglrj");
  byte[] key = Encoding.ASCII.GetBytes("hcxilkqbbhczfeultgbskdmaunivmfuo");            
  CryptoStream cs = new CryptoStream(ms, rijn.CreateEncryptor(key, rgbIV),
           CryptoStreamMode.Write);
  cs.Write(clearTextBytes, 0, clearTextBytes.Length);
  cs.Close();
  return Convert.ToBase64String(ms.ToArray());
}

public static string DecryptString(string EncryptedText)
        {
  byte[] encryptedTextBytes = Convert.FromBase64String(EncryptedText);

  MemoryStream ms = new MemoryStream();

  System.Security.Cryptography.SymmetricAlgorithm rijn = SymmetricAlgorithm.Create();
  rijn.Mode = CipherMode.CFB;

  byte[] rgbIV = Encoding.ASCII.GetBytes("ryojvlzmdalyglrj");
  byte[] key = Encoding.ASCII.GetBytes("hcxilkqbbhczfeultgbskdmaunivmfuo"); ;

  CryptoStream cs = new CryptoStream(ms, rijn.CreateDecryptor(key, rgbIV),
  CryptoStreamMode.Write);

  cs.Write(encryptedTextBytes, 0, encryptedTextBytes.Length);

  cs.Close();

  return Encoding.UTF8.GetString(ms.ToArray());
}

I understood from another post that there is

rijn.Padding = PaddingMode.None;

When I added this I get an error that says "Length of the data to encrypt is invalid"

Even when I try to encrypt a 6 byte string then I see get a long result.

var def1 = Encrypt.EncryptString("abcdefg");

gives me 24 bytes!

Can someone give me some advice here.

UPDATE

Changed to the following:

        byte[] bytOut = ms.GetBuffer();
        int i = 0;
        for (i = 0; i < bytOut.Length; i++)
            if (bytOut[i] == 0)
                break;

        // convert into Base64 so that the result can be used in xml

        return System.Convert.ToBase64String(bytO开发者_JAVA技巧ut, 0, i);

When I check bytOut it's 16bytes Then the value returned after ToBase64 is 24 bytes. I am still not sure why the size is so large

Your problem is the mode of operation. The default is Cipher Block Chaining (CBC), which requires each block match up the block size of the algorithm, and padding to be used if necessary.

You can use another mode. Take CFB for example, it will internally pad your data before doing the plain ECB mode, and cut off the padding when it returns your result. (and do some clever stuff with the IVs so that you can continue to use the cipher without padding.) But it seems suitable for your case.

rijn.Mode = CipherMode.CFB;

Encryption algorithms work in blocks. It will always round up to the nearest block size. You just need a well-defined padding algorithm, so you can correctly remove the padding after decryption.