```
#!/usr/bin/env python3

#importing Bifid
from pycipher import Bifid
from string import *
from pwn import *

#given message:
message="snbwmuotwodwvcywfgmruotoozaiwghlabvuzmfobhtywftopmtawyhifqgtsiowetrksrzgrztkfctxnrswnhxshylyehtatssukfvsnztyzlopsv"

#list that holds all the lines of the rambling file
rambls=[]

#opening the given file and creating a list
with open("ramblings", "r") as file:
pangrams=file.readlines()
for pangram in pangrams:
#removing punctuation, spaces, new lines, and "j" as Bifid ciphers do not involve j
x=pangram.lower().translate(str.maketrans("","",punctuation)).replace(" ", "").replace("\n", "").replace("j", "")
rambls.append(x)

#as the challenge name(difib=>reverse of bifid) suggest the real stuff in this challenge is to reverse the key
for rambl in rambls[::-1]:
#the keys should be less than 25 characters without j
if len(rambl) < 26:
#Bifid(<key>, <period(box grid)>).decipher(<cipher>)
message=Bifid(rambl,5).decipher(message).lower()

#consider x as spaces
print(message.replace("x", " "))#================> ust some unnecessary te t that holds absolutely no meaning whatsoever and bears no significance to you in any way

#so by guessing we can arrive at "just some unnecessary text that holds absolutely no meaning whatsoever and bears no significance to you in any way"

#submit to the gaurd and get the flag \0/
connection=remote("crypto.chal.csaw.io","5004")
connection.sendlineafter("!", "just some unnecessary text that holds absolutely no meaning whatsoever and bears no significance to you in any way")
print(connection.recvall())

```
> [original writeup](https://github.com/rithik2002/CSAW_CTF_2020/blob/master/modulusOPerandi_complete/getFlag.py)