Substitution Cipher Implementation - File Encryption/Decryption



Task

Encrypt a input/source file by replacing every upper/lower case alphabets of the source file with another predetermined upper/lower case alphabets or symbols and save it into another output/encrypted file and then again convert that output/encrypted file into original/decrypted file.

This type of Encryption/Decryption scheme is often called a Substitution Cipher.



Related tasks

 Caesar cipher
 Rot-13
 Vigenère Cipher/Cryptanalysis


See also

 Wikipedia: Substitution cipher


include ..\Utilitys.pmt
 
" ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
" VsciBjedgrzyHalvXZKtUPumGfIwJxqOCFRApnDhQWobLkESYMTN"
"A simple example"
 
def Encode
    >ps
    tps not if >ps swap ps> endif
    len for
        >ps
        tps get swap >ps
        rot swap find
        rot swap get
        ps> swap ps> set
    endfor
    ps> not if >ps swap ps> endif
enddef
 
dup ?
true Encode dup ?
false Encode ?