Cyber-talent secretbox solution secret-box

secretbox-sol.py

#CTF https://cybertalents.com/competitions/quals-uae-egy-national-cyber-security-ctf-2018/secret-box
#https://s3-eu-west-1.amazonaws.com/hubchallenges/Reverse/secretbox.zip
#
#
#The code takes the message
#reveres it
# msg bitwised with the length of image file name
#Each char at i postioton  in the MSG is stored in the image at  postition  [0,i][3]
#
#python secretbox-sol.py secret.png
#
#
import sys
from PIL import Image

def prob(s_img):
        im = Image.open(s_img).convert("RGBA")
        p = im.load()
        c = 0
        lines=''
        for i in range(0, 100):         
                dx=str(p[c, 0][3]) 
                c += 1
                if dx != '255':
                        asc=int(dx)^len(s_img)
                        ec=chr(asc)
                        lines=str(ec)+lines
        print lines
        open('sol.txt','w').write(lines)
prob(sys.argv[1])