basic-mod1

03/29/2022

By: draNx

Tags: crypto PicoCTF-2022

Problem Description:

We found this weird message being passed around on the servers, we think we have a working decryption scheme. Download the message here. Take each number mod 37 and map it to the following character set: 0-25 is the alphabet (uppercase), 26-35 are the decimal digits, and 36 is an underscore. Wrap your decrypted message in the picoCTF flag format (i.e. picoCTF{decrypted_message})

Hints:

Reveal Hints

Do you know what mod 37 means? | mod 37 means modulo 37. It gives the remainder of a number after being divided by 37.

Basic-Mod1

Just do what they tell you to do, example python code below:

message = "91 322 57 124 40 406 272 147 239 285 353 272 77 110 296 262 299 323 255 337 150 102"
alphabet = "abcdefghijklmnopqrstuvwxyz0123456789_"
result = ""
for num in message.split():
    result += alphabet[int(num) % 37]
print(result)

Flag: picoCTF{r0und_n_r0und_(unique code)}