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elliptic-shiho/solve.py

Last active June 11, 2017 16:05
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SHA2017 CTF Teaser: Crypto Engine Solver
Raw
solve.py
from PIL import Image
im = Image.open('flag.png')
pix = im.load()
t = []
for i in xrange(im.size[0] / 40):
t += pix[i*40 + 5, 5]
t += [0x2e, 0x29]
k = [0x32, 0x30, 0x31, 0x37]
s = ''
for i, x in enumerate(t):
s += chr(x ^ k[i % 4])
print repr(s)
prev = ''
res = s[:4]
for i in xrange(0, len(s), 4):
if prev != '':
res += ''.join(map(lambda x: chr(ord(x[0]) ^ ord(x[1])), zip(s[i:i+4], prev)))
prev = s[i:i+4]
print res
Raw
solve_log
Mon Jun 12 01:01:34 JST 2017 ~/ctf/2017/sha2017-ctf 100% Full
> python solve.py
'flag\x1d\x08\x04\x06{1<5\x1eS\x0f\x01{g74\x18\x02\x0eP*ch6\x1a\x02\r\x02.d57\x1c\x19'
flag{deaf983eb34e485ce9d2aff0ae44f852}
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