PicoCTF2022 - rail-fence
Description
A type of transposition cipher is the rail fence cipher, which is described here. Here is one such cipher encrypted using the rail fence with 4 rails. Can you decrypt it? Download the message here. Put the decoded message in the picoCTF flag format, picoCTF{decoded_message}.
Information
Point Value: 100 points
Category: Cryptography
Hints
- Once you've understood how the cipher works, it's best to draw it out yourself on paper.
Solution
We know the text file is encoded using the rail fence cipher, so we open the txt file to obtain the encoded cipher, and use CyberChef to decode it. Entering the encoded cipher from the txt file as the input and using the "Rail Fence Cipher Decode" recipe with a key of 4, we get the output "The flag is: WH3R3_D035_7H3_F3NC3_8361N_4ND_3ND_D00AFDD3". Putting this in the picoCTF flag format we get the flag.