[Ideas] RFC-8452 enhancement with adding "custom-padding" trick and more..

[Shahin Noursalehi <[e-mail]>]

dear madam / sir

during a private research around RFC-8452 (section 9. security
considerations) in response to any "downgrade attacks" with poor legacy
cryptographic algorithms and also poor key management with modern
algorithms that could end at some sort of "padding oracle attacks",  just
added two "custom-padding" phrases, separating with "|" (vertical bar ) to
the left and right sides of any plaintext, before getting processed by ANY
encryption phase. the sample code bellow in C# explains how simple could
this implementation be (in applied implementation we will replace the
mentioned RNG function bellow with robust editions):

// BGN: add custom-padding to the plain_text
public static string custom_padding(string plain_text)
{
   Random rnd = new Random();
  int custom_padding_size_left = rnd.Next(10, 100);
  int custom_padding_size_right = rnd.Next(10, 100);
   string custom_padding_left =  rnd_simple(custom_padding_size_left);
   string custom_padding_right = rnd_simple(custom_padding_size_right);

  string plain_text_with_custom_padding = custom_padding_left + "|" +
plain_text + "|" + custom_padding_right;
}
// END: add custom-padding to the plain_text

// BGN: generate random string for custom-padding
public static string rnd_simple(int size)
{
  var chars =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
  var stringChars = new char[size];
  var random = new Random();

  for (int i = 0; i < stringChars.Length; i++)
  {
    stringChars[i] = chars[random.Next(chars.Length)];
  }

  var finalString = new String(stringChars);
  return finalString;
}
// END: generate random string for custom-padding


after the decryption phase, the added "custom-padding" phrases could get
clear by addressing those vertical bars (|). so, because of the benefits I
could see in this approach with many cryptographic algorithms (including
RFC-8452), just decided to send this idea to the respected members of IETF
for more evaluation and suggestions.

any feedback welcome,
--shahiN Noursalehi