PicoCTF2022 - transposition-trial

Description

Our data got corrupted on the way here. Luckily, nothing got replaced, but every block of 3 got scrambled around! The first word seems to be three letters long, maybe you can use that to recover the rest of the message. Download the corrupted message here.

Information

Point Value: 100 points

Category: Cryptography

Hints

1. Split the message up into blocks of 3 and see how the first block is scrambled

Solution

Opening up the text file, we see the corrupted message as "heTfl g as iicpCTo{7F4NRP051N5_16_35P3X51N3_V9AAB1F8}7". The first three letters are "heT", which must be the word "The". We see then that the pattern of unscrambling is taking the last letter and putting it back in the front. We can do this manually or write a simple program to unscramble it for us. Running the following Python program gives us the flag. with open('transpositionTrial.txt') as f:
    message = f.readline()

newMessage = ""

for x in range(0, len(message), 3):
    newMessage += message[x+2:x+3] + message[x:x+2]

print(newMessage)

Flag