def challenge_6():
with open('6.txt') as f:
data = base64.b64decode(f.read())
keysize_candidates = list()
for keysize in range(1, 30):
chunks = chunk_into(data, keysize)
pairs = itertools.combinations(chunks[:4], 2)
score = 0
for a, b in pairs:
hscore = hamming(a, b)
logger.debug(hscore)
score += hscore / keysize
score /= 4
keysize_candidates.append((keysize, score))
keysize_probability = sorted(keysize_candidates, key=lambda x: x[1])
logger.info("Probable keysizes: {}".format(keysize_probability[:5]))
for keysize, score in keysize_probability[:3]:
key_ints = list()
logger.debug(keysize)
chunks = chunk_into(data, keysize)
transposed = zip(*chunks[:-1])
for c in transposed:
try:
_, key_int = english_freq(bytes(c))
key_ints.append(key_int)
except TypeError:
break
if len(key_ints) == keysize:
return xor_with_key(data, bytes(key_ints))
def test_challenge_5(self):
data = b"""Burning 'em, if you ain't quick and nimble
I go crazy when I hear a cymbal"""
output = binascii.unhexlify("0b3637272a2b2e63622c2e69692a23693a2a3c6324202d623d63343c2a26226324272765272"
"a282b2f20430a652e2c652a3124333a653e2b2027630c692b20283165286326302e27282f")
key = b'ICE'
self.assertEqual(output, xor_with_key(data, key))
def challenge_6():
with open('6.txt') as f:
data = base64.b64decode(f.read())
keysize_candidates = list()
for keysize in range(1, 30):
chunks = chunk_into(data, keysize)
pairs = itertools.combinations(chunks[:4], 2)
score = 0
for a, b in pairs:
hscore = hamming(a, b)
logger.debug(hscore)
score += hscore / keysize
score /= 4
keysize_candidates.append((keysize, score))
keysize_probability = sorted(keysize_candidates, key=lambda x: x[1])
logger.info("Probable keysizes: {}".format(keysize_probability[:5]))
for keysize, score in keysize_probability[:3]:
key_ints = list()
logger.debug(keysize)
chunks = chunk_into(data, keysize)
transposed = zip(*chunks[:-1])
for c in transposed:
try:
_, key_int = english_freq(bytes(c))
key_ints.append(key_int)
except TypeError:
break
if len(key_ints) == keysize:
return xor_with_key(data, bytes(key_ints))
def decrypt(self, data):
assert len(data) % 16 == 0
blocks = chunk_into(data, 16)
plain = list()
for block in blocks:
plain.append(xor_with_key(ECB(self.key).decrypt(block), self._state))
self._state = block
return unpad(b''.join(plain))
def main():
piecemeal = [bytes(x) for x in zip(*CIPHERTEXTS)]
keystream = list()
for x in piecemeal:
c = english_freq(x)
keystream.append(c[1])
for ct in CIPHERTEXTS:
logger.info(xor_with_key(ct, bytes(keystream)))
def encrypt(self, data):
ret = list()
blocks = chunk_into(data, BLOCKSIZE)
for i, block in enumerate(blocks):
_ks = self.cipher.encrypt(struct.pack('<2Q', self.nonce, i))
logger.debug(block)
logger.debug(_ks)
ret.append(xor_with_key(block, _ks))
return b''.join(ret)
def decrypt(self, data):
assert len(data) % 16 == 0
blocks = chunk_into(data, 16)
plain = list()
for block in blocks:
plain.append(
xor_with_key(ECB(self.key).decrypt(block), self._state))
self._state = block
return unpad(b''.join(plain))
def encrypt(self, data):
ret = list()
blocks = chunk_into(data, BLOCKSIZE)
for i, block in enumerate(blocks):
_ks = self.cipher.encrypt(struct.pack('<2Q', self.nonce, i))
logger.debug(block)
logger.debug(_ks)
ret.append(xor_with_key(block, _ks))
return b''.join(ret)
def test_challenge_5(self):
data = b"""Burning 'em, if you ain't quick and nimble
I go crazy when I hear a cymbal"""
output = binascii.unhexlify(
"0b3637272a2b2e63622c2e69692a23693a2a3c6324202d623d63343c2a26226324272765272"
"a282b2f20430a652e2c652a3124333a653e2b2027630c692b20283165286326302e27282f"
)
key = b'ICE'
self.assertEqual(output, xor_with_key(data, key))
def encrypt(self, data):
if not len(data) % 16 == 0:
data = pkcs7pad(data, 16)
blocks = chunk_into(data, 16)
ciphertext = list()
for block in blocks:
cipherblock = ECB(self.key).encrypt(xor_with_key(block, self._state))
ciphertext.append(cipherblock)
self._state = cipherblock
return b''.join(ciphertext)
def encrypt(self, data):
if not len(data) % 16 == 0:
data = pkcs7pad(data, 16)
blocks = chunk_into(data, 16)
ciphertext = list()
for block in blocks:
cipherblock = ECB(self.key).encrypt(
xor_with_key(block, self._state))
ciphertext.append(cipherblock)
self._state = cipherblock
return b''.join(ciphertext)
def main():
"""
This actually solves Challenge 19 as Challenge 20 is meant to be solved.
Deal with it :D
:return:
"""
ciphertexts = encrypt()
l = len(max(ciphertexts, key=len))
keystream = list()
for x in range(l):
z = bytes(ct[x] for ct in ciphertexts if len(ct) > x)
c = english_freq(z)
logger.fatal(c)
keystream.append(c[1])
for ct in ciphertexts:
logger.info(xor_with_key(ct, bytes(keystream)))
def main():
"""
This actually solves Challenge 19 as Challenge 20 is meant to be solved.
Deal with it :D
:return:
"""
ciphertexts = encrypt()
l = len(max(ciphertexts, key=len))
keystream = list()
for x in range(l):
z = bytes(ct[x] for ct in ciphertexts if len(ct) > x)
c = english_freq(z)
logger.fatal(c)
keystream.append(c[1])
for ct in ciphertexts:
logger.info(xor_with_key(ct, bytes(keystream)))
def challenge_15():
idxs = (0, 6, 11, 13)
flipper = bytearray(16)
inject = b':admin<true:x<'
for i in idxs:
flipper[i] = 1
for i in range(0, BLOCKSIZE):
ct = c15_enc(b'x' * i + inject)
paste = xor_with_key(ct[32:48], flipper)
new_ct = ct[:32] + paste + ct[48:]
if c15_verify(new_ct):
return True
else:
logger.fatal('Bitflip attack failed')
ct = c15_enc(inject)
return c15_verify(ct)
