def detect_potential_repeating_ecb_blocks(ciphertext, blocksize=16):
seen = set()
for block in brake_into_keysize_blocks(ciphertext, blocksize):
if block in seen:
return True
else:
seen.add(block)
return False
def cbc_encrypt(key, iv, plaintext):
blocks = brake_into_keysize_blocks(pad_pkcs_7(plaintext, 16), 16)
cipher = AES.new(key, AES.MODE_ECB)
def cryptoblocks():
last_block = iv
for block in blocks:
chained = xor_buffers(last_block, block)
last_block = cipher.encrypt(chained)
yield last_block
return b''.join([cb for cb in cryptoblocks()])
def cbc_decrypt(key, iv, ciphertext):
assert len(ciphertext) % 16 == 0
blocks = brake_into_keysize_blocks(ciphertext, 16)
cipher = AES.new(key, AES.MODE_ECB)
def plainblocks():
last_block = iv
for block in blocks:
decrypted_block = cipher.decrypt(block)
plain_block = xor_buffers(last_block, decrypted_block)
last_block = block
yield plain_block
return strip_pkcs_7(b''.join(pb for pb in plainblocks()))
def _guess_xor_key_for_given_size(ciphertext, size):
sections = _transpose_blocks(brake_into_keysize_blocks(ciphertext, size))
decryptions = [break_single_byte_xor(section) for section in sections]
key_bytes = (decryption[0] for decryption in decryptions)
return b"".join(key_bytes)
def test_rest(self):
assert bf.brake_into_keysize_blocks(b"blablobl", 3) == \
[b"bla", b"blo", b"bl"]
def test_example(self):
assert bf.brake_into_keysize_blocks(b"blablobliblu", 3) == \
[b"bla", b"blo", b"bli", b"blu"]