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Solution for white box from RHME3 Qualifier.
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from array import array | |
# 2^16 bytes of dumped memory from 0x6651C0 | |
# create as follows: gdb ./whitebox -ex 'br *0x4007fd' -ex r -ex 'dump memory tab.bin 0x6651c0 0x6651c0+0x10000' -ex q | |
tab = array('B',open('tab.bin').read()) | |
sbox = array('B', | |
'637c777bf26b6fc53001672bfed7ab76ca82c97dfa5947f0add4a2af9ca472c0' | |
'b7fd9326363ff7cc34a5e5f171d8311504c723c31896059a071280e2eb27b275' | |
'09832c1a1b6e5aa0523bd6b329e32f8453d100ed20fcb15b6acbbe394a4c58cf' | |
'd0efaafb434d338545f9027f503c9fa851a3408f929d38f5bcb6da2110fff3d2' | |
'cd0c13ec5f974417c4a77e3d645d197360814fdc222a908846eeb814de5e0bdb' | |
'e0323a0a4906245cc2d3ac629195e479e7c8376d8dd54ea96c56f4ea657aae08' | |
'ba78252e1ca6b4c6e8dd741f4bbd8b8a703eb5664803f60e613557b986c11d9e' | |
'e1f8981169d98e949b1e87e9ce5528df8ca1890dbfe6426841992d0fb054bb16'.decode('hex')) | |
K = [] | |
for i in range(0x10): | |
for a in range(0x100): | |
keys = set() | |
for j in range(0x100): | |
k = sbox[j^a] ^ tab[i*256+j] | |
keys.add(k) | |
if len(keys)==1: | |
K.append(k) | |
assert len(K) == 16 | |
rcon = [0, 1, 2, 4, 8, 16, 32, 64, 128, 27, 54] | |
def invert_keyschedule(key, round): | |
for i in range(round, 0, -1): | |
for j in range(15, 3, -1): | |
key[j] ^= key[j-4] | |
for j in range(3, -1, -1): | |
key[j] ^= sbox[key[12+(j+1)%4]] ^ (0 if j else rcon[i]) | |
return key | |
print array('B',invert_keyschedule(K, 10)).tostring() |
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