Keyless ciphers ROT13 / 47 ilk

It looks like you might be looking for some "classic crypto" solutions.

KYPER SUBSTITUTION are encodings in which one character is replaced by another. For example. A-> Y, B-> Q, C-> P, etc. The "Caesar cipher" is a special case where the order is stored and the "key" is the offset. In the case of rot13 / 47, the "key" is 13 or 47 respectively, although it could be something like 3 (A-> D, B-> E, C-> F, ...).

TRANSPOSITION CIPHERS are those that do not replace letters, but letters that rearrange the letters in a predetermined way. For example:

CRYPTOGRAPHY

      

        
        
        
      

    

can be written as

C Y T G A H
 R P O R P Y

      

        
        
        
      

    

So the encrypted output is created by reading two lines from left to right

CYTGAHRPORPY

      

        
        
        
      

    

Another property of rot13 / 47 is that it is REVERSABLE:

encode(encode(plaintext)) == plaintext

      

        
        
        
      

    

If this is the property you want, you can simply pass the XOR message with the known (previously accepted) XOR value. Then XOR the ciphertext with the same value will return the original text. An example of this would be the memfrob function , which simply XOR creates a buffer with the binary representation of 42.

You can also check other forms of ENCODINGS like Base64 if this is closer to what you are looking for.

!! Disclaimer - If you have data that you are actually trying to protect from someone else, do not use any of these methods. While entertaining, all of these methods are trivial to break.