basic-mod1

Challenge Description

The approach for this challenge was already provided in the description, so we can just follow that.

The contents of message.txt

After downloading the file using wget, and running cat message.txt, we get this string of numbers:

165 248 94 346 299 73 198 221 313 137 205 87 336 110 186 69 223 213 216 216 177 138

Decrypting the Message

Decryption Script

I used a python script to decrypt the message above in order to get the flag. The following shows my code.

# Based on the specifications in the challenge description
chrs = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_"
 
enc_message = "165 248 94 346 299 73 198 221 313 137 205 87 336 110 186 69 223 213 216 216 177 138"
 
flag = "" 
 
for i in enc_message.split():
  mod37 = int(i) % 37
  dec_chr = chrs[mod37]
  flag += dec_chr
 
print(flag)

Flag

picoCTF{R0UND_N_R0UND_B6B25531}