# An XOR alternative

# cat xor_alternative.py
import sys

# data contains hex chars (a-f + 0-9) and random chars
# Chars are not repeated
data = '2ubfLkR0vsJ#)=SQtXNcO6AYPT1U+ja7W*h9I-y4GeHzn5&BK;_@$U3dm8^%'

def obfuscate(s, step):
 out = ''
 ldata = len(data)
 ls = len(s)
 for i in s:
  h = hex(ord(i))[2:]
  for j in h:
   p = data.index(j)
   p2 = (p + step) % ldata
   out += data[p2]
 return out

def deobfuscate(s, step):
 out = ''
 ldata = len(data)
 ls = len(s)
 for i in range(0, ls, 2):
  h = ''
  for j in range(2):
   p = data.index(s[i + j])
   p2 = (p - step) % ldata
   h += data[p2]
  out += chr(int(h, 16))
 return out

action = sys.argv[1]
s = sys.argv[2]
step = int(sys.argv[3])

print 'String =', s
print 'Step =', step

if action == 'o':
 print 'Action = Obfuscate'
 print 'Result =', obfuscate(s, step)
elif action == 'd':
 print 'Action = Deobfuscate'
 print 'Result =', deobfuscate(s, step)

# python xor_alternative.py o SECRET 1234
String = SECRET
Step = 1234
Action = Obfuscate
Result = c+=c=+ch=cc=

# python xor_alternative.py d c+=c=+ch=cc= 1234
String = c+=c=+ch=cc=
Step = 1234
Action = Deobfuscate
Result = SECRET

Reference

https://isc.sans.edu/forums/diary/Obfuscating+without+XOR/22544/

# GynvaelEN mission 006

# cat mission_06.py
from PIL import Image
import qrtools

n = 25
m = 3
fn = 'mission_06.png'

matrix = [255 for i in range(n * n)]

with open('mission_06.data') as f:
 data = f.read().splitlines()

for line in data:
 line = line[1:-1].split(', ')
 i = int(line[0])
 j = int(line[1])
 matrix[(i*n) + j] = 0

image = Image.new('L', (n, n))
image.putdata(matrix)
image.save(fn)

img = Image.open(fn)
img = img.rotate(-90)
img = img.resize((n * m, n * m), Image.ANTIALIAS)
img.save(fn)

qr = qrtools.QR(filename = fn)
if qr.decode():
 print qr.data

# python mission_06.py
Mirrored QR? Seriously?!

Source

https://www.youtube.com/watch?v=KvyBn4Btv8E (1:32:02)

# GynvaelEN mission 005

# curl -v http://gynvael.vexillium.org/ext/thepicture/picture.image
Content-Encoding: rle
Content-Type: image/raw; w=640,h=212,bpp=8
# cat mission_05.py
from struct import unpack
from PIL import Image

with open('picture.image') as f:
 cdata = f.read()

ddata = []

for i in range(0, len(cdata), 2):
 v = unpack('B', cdata[i + 1])[0] ^ 1
 for _ in range(unpack('B', cdata[i])[0]):
  ddata.append(v * 255)

image = Image.new('L', (640, 212))
image.putdata(ddata)
image.save('output.png')
# python mission_05.py

Source

https://www.youtube.com/watch?v=W7s5CWaw6I4 (1:20:57)

Reference

https://en.wikipedia.org/wiki/Run-length_encoding