238 lines
8.6 KiB
Python
238 lines
8.6 KiB
Python
|
# -*- coding: utf-8 -*-
|
||
|
|
#
|
||
|
|
# Cipher/DES3.py : DES3
|
||
|
|
#
|
||
|
|
# ===================================================================
|
||
|
|
# The contents of this file are dedicated to the public domain. To
|
||
|
|
# the extent that dedication to the public domain is not available,
|
||
|
|
# everyone is granted a worldwide, perpetual, royalty-free,
|
||
|
|
# non-exclusive license to exercise all rights associated with the
|
||
|
|
# contents of this file for any purpose whatsoever.
|
||
|
|
# No rights are reserved.
|
||
|
|
#
|
||
|
|
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
|
||
|
|
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
|
||
|
|
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
|
||
|
|
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
|
||
|
|
# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
|
||
|
|
# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
|
||
|
|
# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
|
||
|
|
# SOFTWARE.
|
||
|
|
# ===================================================================
|
||
|
|
"""Triple DES symmetric cipher
|
||
|
|
|
||
|
|
`Triple DES`__ (or TDES or TDEA or 3DES) is a symmetric block cipher
|
||
|
|
standardized by NIST_. It has a fixed data block size of 8 bytes.
|
||
|
|
|
||
|
|
TDES consists of the concatenation of 3 simple Single `DES` ciphers
|
||
|
|
(encryption - decryption - encryption), where each stage uses an
|
||
|
|
indipendent sub-key.
|
||
|
|
|
||
|
|
A TDES key is therefore 24 (8+8+8) bytes long. However, like Single DES,
|
||
|
|
only 7 out of 8 bits are actually used: the remaining ones are parity
|
||
|
|
bits (which practically all TDES implementations ignore).
|
||
|
|
Theoreticaly, Triple DES achieves up to 112 bits of effective security.
|
||
|
|
|
||
|
|
Triple DES can also operate with a 16 bytes key (Option 2, also termed 2TDES),
|
||
|
|
in which case subkey *K1* equals subkey *K2*. The effective security
|
||
|
|
is as low as `90 bits`_.
|
||
|
|
|
||
|
|
Thi implementation checks and enforces the condition *K1 != K2 != K3*
|
||
|
|
(Option 3), as it degrades Triple DES to Single DES.
|
||
|
|
|
||
|
|
*Use AES, not TDES. This module is provided for legacy purposes only.**
|
||
|
|
|
||
|
|
As an example, encryption can be done as follows:
|
||
|
|
|
||
|
|
>>> from Crypto.Cipher import DES3
|
||
|
|
>>> from Crypto.Random import get_random_bytes
|
||
|
|
>>>
|
||
|
|
>>> # When generating a Triple DES key you must check that
|
||
|
|
>>> # subkey1 != subkey2 and subkey2 != subkey3
|
||
|
|
>>> while True:
|
||
|
|
>>> try:
|
||
|
|
>>> key = DES3.adjust_key_parity(get_random_bytes(24))
|
||
|
|
>>> break
|
||
|
|
>>> except ValueError
|
||
|
|
>>> pass
|
||
|
|
>>>
|
||
|
|
>>> cipher = DES3.new(key, DES3.MODE_CFB)
|
||
|
|
>>> plaintext = b'We are no longer the knights who say ni!'
|
||
|
|
>>> msg = cipher.nonce + cipher.encrypt(plaintext)
|
||
|
|
|
||
|
|
.. __: http://en.wikipedia.org/wiki/Triple_DES
|
||
|
|
.. _NIST: http://csrc.nist.gov/publications/nistpubs/800-67-Rev1/SP-800-67-Rev1.pdf
|
||
|
|
.. _90 bits: http://people.scs.carleton.ca/~paulv/papers/Euro90.pdf
|
||
|
|
|
||
|
|
:undocumented: __package__
|
||
|
|
"""
|
||
|
|
|
||
|
|
import sys
|
||
|
|
|
||
|
|
from Crypto.Cipher import _create_cipher
|
||
|
|
from Crypto.Util.py3compat import byte_string, b, bchr, bord
|
||
|
|
from Crypto.Util._raw_api import (load_pycryptodome_raw_lib,
|
||
|
|
VoidPointer, SmartPointer,
|
||
|
|
c_size_t, expect_byte_string)
|
||
|
|
|
||
|
|
_raw_des3_lib = load_pycryptodome_raw_lib(
|
||
|
|
"Crypto.Cipher._raw_des3",
|
||
|
|
"""
|
||
|
|
int DES3_start_operation(const uint8_t key[],
|
||
|
|
size_t key_len,
|
||
|
|
void **pResult);
|
||
|
|
int DES3_encrypt(const void *state,
|
||
|
|
const uint8_t *in,
|
||
|
|
uint8_t *out,
|
||
|
|
size_t data_len);
|
||
|
|
int DES3_decrypt(const void *state,
|
||
|
|
const uint8_t *in,
|
||
|
|
uint8_t *out,
|
||
|
|
size_t data_len);
|
||
|
|
int DES3_stop_operation(void *state);
|
||
|
|
""")
|
||
|
|
|
||
|
|
|
||
|
|
def adjust_key_parity(key_in):
|
||
|
|
"""Return the TDES key with parity bits correctly set"""
|
||
|
|
|
||
|
|
def parity_byte(key_byte):
|
||
|
|
parity = 1
|
||
|
|
for i in range(1, 8):
|
||
|
|
parity ^= (key_byte >> i) & 1
|
||
|
|
return (key_byte & 0xFE) | parity
|
||
|
|
|
||
|
|
if len(key_in) not in key_size:
|
||
|
|
raise ValueError("Not a valid TDES key")
|
||
|
|
|
||
|
|
key_out = b("").join([ bchr(parity_byte(bord(x)) )for x in key_in ])
|
||
|
|
|
||
|
|
if key_out[:8] == key_out[8:16] or key_out[-16:-8] == key_out[-8:]:
|
||
|
|
raise ValueError("Triple DES key degenerates to single DES")
|
||
|
|
|
||
|
|
return key_out
|
||
|
|
|
||
|
|
|
||
|
|
def _create_base_cipher(dict_parameters):
|
||
|
|
"""This method instantiates and returns a handle to a low-level base cipher.
|
||
|
|
It will absorb named parameters in the process."""
|
||
|
|
|
||
|
|
try:
|
||
|
|
key_in = dict_parameters.pop("key")
|
||
|
|
except KeyError:
|
||
|
|
raise TypeError("Missing 'key' parameter")
|
||
|
|
|
||
|
|
key = adjust_key_parity(key_in)
|
||
|
|
|
||
|
|
start_operation = _raw_des3_lib.DES3_start_operation
|
||
|
|
stop_operation = _raw_des3_lib.DES3_stop_operation
|
||
|
|
|
||
|
|
cipher = VoidPointer()
|
||
|
|
result = start_operation(key,
|
||
|
|
c_size_t(len(key)),
|
||
|
|
cipher.address_of())
|
||
|
|
if result:
|
||
|
|
raise ValueError("Error %X while instantiating the TDES cipher"
|
||
|
|
% result)
|
||
|
|
return SmartPointer(cipher.get(), stop_operation)
|
||
|
|
|
||
|
|
|
||
|
|
def new(key, mode, *args, **kwargs):
|
||
|
|
"""Create a new TDES cipher
|
||
|
|
|
||
|
|
:Parameters:
|
||
|
|
key : byte string
|
||
|
|
The secret key to use in the symmetric cipher.
|
||
|
|
It must be 16 or 24 bytes long. The parity bits will be ignored.
|
||
|
|
The condition K1 != K2 != K3 must hold.
|
||
|
|
|
||
|
|
mode : a *MODE_** constant
|
||
|
|
The chaining mode to use for encryption or decryption.
|
||
|
|
|
||
|
|
:Keywords:
|
||
|
|
iv : byte string
|
||
|
|
(*Only* `MODE_CBC`, `MODE_CFB`, `MODE_OFB`, `MODE_OPENPGP`).
|
||
|
|
|
||
|
|
The initialization vector to use for encryption or decryption.
|
||
|
|
|
||
|
|
For `MODE_OPENPGP`, IV must be 8 bytes long for encryption
|
||
|
|
and 10 bytes for decryption (in the latter case, it is
|
||
|
|
actually the *encrypted* IV which was prefixed to the ciphertext).
|
||
|
|
|
||
|
|
For all other modes, it must be 8 bytes long.
|
||
|
|
|
||
|
|
If not provided, a random byte string will be generated (you can read
|
||
|
|
it back via the ``iv`` attribute).
|
||
|
|
|
||
|
|
nonce : byte string
|
||
|
|
(*Only* `MODE_EAX` and `MODE_CTR`)
|
||
|
|
A value that must never be reused for any other encryption.
|
||
|
|
|
||
|
|
For `MODE_CTR`, its length must be in the range ``[0..7]``.
|
||
|
|
|
||
|
|
For `MODE_EAX`, there are no restrictions, but it is recommended to
|
||
|
|
use at least 16 bytes.
|
||
|
|
|
||
|
|
If not provided for `MODE_EAX`, a random 16 byte string is generated
|
||
|
|
(you can read it back via the ``nonce`` attribute).
|
||
|
|
|
||
|
|
mac_len : integer
|
||
|
|
(*Only* `MODE_EAX`). Length of the authentication tag, in bytes.
|
||
|
|
It must be no larger than 8 (which is the default).
|
||
|
|
|
||
|
|
segment_size : integer
|
||
|
|
(*Only* `MODE_CFB`).The number of **bits** the plaintext and ciphertext
|
||
|
|
are segmented in. It must be a multiple of 8.
|
||
|
|
If not specified, it will be assumed to be 8.
|
||
|
|
|
||
|
|
initial_value : integer
|
||
|
|
(*Only* `MODE_CTR`). The initial value for the counter within
|
||
|
|
the counter block. By default it is 0.
|
||
|
|
|
||
|
|
:Attention: it is important that all 8 byte subkeys are different,
|
||
|
|
otherwise TDES would degrade to single `DES`.
|
||
|
|
|
||
|
|
:Raise ValueError:
|
||
|
|
when the key degrades to Single DES.
|
||
|
|
|
||
|
|
:Return: a DES cipher object, of the applicable mode:
|
||
|
|
|
||
|
|
- CBC_ mode
|
||
|
|
- CFB_ mode
|
||
|
|
- CTR_ mode
|
||
|
|
- EAX_ mode
|
||
|
|
- ECB_ mode
|
||
|
|
- OFB_ mode
|
||
|
|
- OpenPgp_ mode
|
||
|
|
|
||
|
|
.. _CBC: Crypto.Cipher._mode_cbc.CbcMode-class.html
|
||
|
|
.. _CFB: Crypto.Cipher._mode_cfb.CfbMode-class.html
|
||
|
|
.. _CTR: Crypto.Cipher._mode_ctr.CtrMode-class.html
|
||
|
|
.. _EAX: Crypto.Cipher._mode_eax.EaxMode-class.html
|
||
|
|
.. _ECB: Crypto.Cipher._mode_ecb.EcbMode-class.html
|
||
|
|
.. _OFB: Crypto.Cipher._mode_ofb.OfbMode-class.html
|
||
|
|
.. _OpenPgp: Crypto.Cipher._mode_openpgp.OpenPgpMode-class.html
|
||
|
|
"""
|
||
|
|
|
||
|
|
return _create_cipher(sys.modules[__name__], key, mode, *args, **kwargs)
|
||
|
|
|
||
|
|
#: Electronic Code Book (ECB). See `Crypto.Cipher._mode_ecb.EcbMode`.
|
||
|
|
MODE_ECB = 1
|
||
|
|
#: Cipher-Block Chaining (CBC). See `Crypto.Cipher._mode_cbc.CbcMode`.
|
||
|
|
MODE_CBC = 2
|
||
|
|
#: Cipher FeedBack (CFB). See `Crypto.Cipher._mode_cfb.CfbMode`.
|
||
|
|
MODE_CFB = 3
|
||
|
|
#: Output FeedBack (OFB). See `Crypto.Cipher._mode_ofb.OfbMode`.
|
||
|
|
MODE_OFB = 5
|
||
|
|
#: CounTer Mode (CTR). See `Crypto.Cipher._mode_ctr.CtrMode`.
|
||
|
|
MODE_CTR = 6
|
||
|
|
#: OpenPGP Mode. See `Crypto.Cipher._mode_openpgp.OpenPgpMode`.
|
||
|
|
MODE_OPENPGP = 7
|
||
|
|
#: EAX Mode. See `Crypto.Cipher._mode_eax.EaxMode`.
|
||
|
|
MODE_EAX = 9
|
||
|
|
|
||
|
|
#: Size of a data block (in bytes)
|
||
|
|
block_size = 8
|
||
|
|
#: Size of a key (in bytes)
|
||
|
|
key_size = (16, 24)
|