def challenge20(path: str) -> bool:
with open(path) as f:
lines = f.readlines()
plain_texts = [base64.b64decode(s) for s in lines]
secrets = []
for i in range(len(plain_texts)):
ctr = AESCipher(AESCipher.MODE_CTR, _KEY, nonce=_NONCE)
secrets.append(ctr.encrypt(plain_texts[i]))
max_len = max(len(s) for s in secrets)
keystream = bytearray()
for i in range(max_len):
i = len(keystream)
char_chain = bytes([s[i] for s in secrets if len(s) > i])
possible_keys = rank_xor_single_byte_key(char_chain)
key_byte = possible_keys[_FIX_MAP.get(i, 0)]
keystream += key_byte
pt = [xor_byte_arrays(s, keystream) for s in secrets]
if pt == plain_texts:
return True
return False
def _edit(cipher_text: bytes, offset: int, new_text: bytes) -> bytes:
ctr = AESCipher(AESCipher.MODE_CTR, _KEY, nonce=_NONCE)
plain_text = ctr.decrypt(cipher_text)
plain_text = plain_text[:offset] + new_text + plain_text[offset +
len(new_text):]
return ctr.encrypt(plain_text)
def encrypt_msg(self, msg: bytes) -> Tuple[bytes, bytes]:
key = sha1(
self._session_key.to_bytes(
floor(self._session_key.bit_length() / 8) + 1, "big"))[:16]
iv = gen_random_bytes(16)
cbc = AESCipher(AESCipher.MODE_CBC, key, iv=iv)
return (iv, cbc.encrypt(pkcs7_pad(msg)))
def _encryption_oracle(bytes_: bytes) -> Tuple[bytes, str]:
key = gen_random_bytes(16)
iv = gen_random_bytes(16)
prefix = gen_random_bytes(random.randint(5, 10))
suffix = gen_random_bytes(random.randint(5, 10))
pt = prefix + bytes_ + suffix
cbc_mode = random.choice([True, False])
if cbc_mode:
cbc = AESCipher(AESCipher.MODE_CBC, key, iv=iv)
ct = cbc.encrypt(pkcs7_pad(pt))
answer = "cbc"
else:
ecb = AESCipher(AESCipher.MODE_ECB, key)
ct = ecb.encrypt(pkcs7_pad(pt))
answer = "ecb"
return ct, answer
def _encrypt_it(path: str) -> (bytes, bytes):
ecb = AESCipher(AESCipher.MODE_ECB, key=b"YELLOW SUBMARINE")
with open(path) as f:
cipher_text = base64.b64decode(f.read())
plain_text = ecb.decrypt(cipher_text)
ctr = AESCipher(AESCipher.MODE_CTR, _KEY, nonce=_NONCE)
cipher_text = ctr.encrypt(plain_text)
return cipher_text, plain_text
def test_aes_ecb_encrypt(self):
# Test vectors from NIST Special Publication 800-38A 2001 Edition
key = bytes.fromhex("2b7e151628aed2a6abf7158809cf4f3c")
pt = bytes.fromhex("6bc1bee22e409f96e93d7e117393172a"
"ae2d8a571e03ac9c9eb76fac45af8e51"
"30c81c46a35ce411e5fbc1191a0a52ef"
"f69f2445df4f9b17ad2b417be66c3710")
ct = bytes.fromhex("3ad77bb40d7a3660a89ecaf32466ef97"
"f5d3d58503b9699de785895a96fdbaaf"
"43b1cd7f598ece23881b00e3ed030688"
"7b0c785e27e8ad3f8223207104725dd4")
ecb = AESCipher(AESCipher.MODE_ECB, key)
result = ecb.encrypt(pt)
assert result == ct, "The result does not match the expected value"
def test_aes_cbc_encrypt(self):
# Test vectors from NIST Special Publication 800-38A 2001 Edition
key = bytes.fromhex("2b7e151628aed2a6abf7158809cf4f3c")
iv = bytes.fromhex("000102030405060708090a0b0c0d0e0f")
pt = bytes.fromhex("6bc1bee22e409f96e93d7e117393172a"
"ae2d8a571e03ac9c9eb76fac45af8e51"
"30c81c46a35ce411e5fbc1191a0a52ef"
"f69f2445df4f9b17ad2b417be66c3710")
ct = bytes.fromhex("7649abac8119b246cee98e9b12e9197d"
"5086cb9b507219ee95db113a917678b2"
"73bed6b8e3c1743b7116e69e22229516"
"3ff1caa1681fac09120eca307586e1a7")
cbc = AESCipher(AESCipher.MODE_CBC, key, iv=iv)
result = cbc.encrypt(pt)
assert result == ct, "The result does not match the expected value"
def challenge19() -> bool:
secrets = []
for i in range(len(_STRINGS)):
ctr = AESCipher(AESCipher.MODE_CTR, _KEY, nonce=_NONCE)
secrets.append(ctr.encrypt(_STRINGS[i]))
max_len = max(len(s) for s in secrets)
keystream = bytearray()
for i in range(max_len):
char_chain = bytes([s[i] for s in secrets if len(s) > i])
possible_keys = rank_xor_single_byte_key(char_chain)
key_byte = possible_keys[_FIX_MAP.get(i, 0)]
keystream += key_byte
pt = [xor_byte_arrays(s, keystream) for s in secrets]
if pt == _STRINGS:
return True
return False
def test_aes_ctr_encrypt(self):
key = bytes.fromhex("2b7e151628aed2a6abf7158809cf4f3c")
nonce = bytes.fromhex("f0f1f2f3f4f5f6f7")
counter = 0xF8F9FAFBFCFDFEFF
pt = bytes.fromhex("6bc1bee22e409f96e93d7e117393172a"
"ae2d8a571e03ac9c9eb76fac45af8e51"
"30c81c46a35ce411e5fbc1191a0a52ef"
"f69f2445df4f9b17ad2b417be66c3710")
ct = bytes.fromhex("874d6191b620e3261bef6864990db6ce"
"9806f66b7970fdff8617187bb9fffdff"
"5ae4df3edbd5d35e5b4f09020db03eab"
"1e031dda2fbe03d1792170a0f3009cee")
cbc = AESCipher(
AESCipher.MODE_CTR,
key,
nonce=nonce,
counter=counter,
counter_byteorder="big",
)
result = cbc.encrypt(pt)
assert result == ct, "The result does not match the expected value"
def _encrypt(pt: bytes) -> (bytes, bytes):
iv = gen_random_bytes(16)
cbc = AESCipher(AESCipher.MODE_CBC, _KEY, iv=iv)
ct = cbc.encrypt(pkcs7_pad(pt))
return iv, ct