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# -*- 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
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# ===================================================================
"""
Module's constants for the modes of operation supported with Triple DES:
:var MODE_ECB: :ref:`Electronic Code Book (ECB) <ecb_mode>`
:var MODE_CBC: :ref:`Cipher-Block Chaining (CBC) <cbc_mode>`
:var MODE_CFB: :ref:`Cipher FeedBack (CFB) <cfb_mode>`
:var MODE_OFB: :ref:`Output FeedBack (OFB) <ofb_mode>`
:var MODE_CTR: :ref:`CounTer Mode (CTR) <ctr_mode>`
:var MODE_OPENPGP: :ref:`OpenPGP Mode <openpgp_mode>`
:var MODE_EAX: :ref:`EAX Mode <eax_mode>`
"""
import sys
from Crypto.Cipher import _create_cipher
from Crypto.Util.py3compat import byte_string, bchr, bord, bstr
from Crypto.Util._raw_api import (load_pycryptodome_raw_lib,
VoidPointer, SmartPointer,
c_size_t)
_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):
"""Set the parity bits in a TDES key.
:param key_in: the TDES key whose bits need to be adjusted
:type key_in: byte string
:returns: a copy of ``key_in``, with the parity bits correctly set
:rtype: byte string
:raises ValueError: if the TDES key is not 16 or 24 bytes long
:raises ValueError: if the TDES key degenerates into Single DES
"""
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(bstr(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 Triple DES cipher.
:param key:
The secret key to use in the symmetric cipher.
It must be 16 or 24 byte long. The parity bits will be ignored.
:type key: bytes/bytearray/memoryview
:param mode:
The chaining mode to use for encryption or decryption.
:type mode: One of the supported ``MODE_*`` constants
:Keyword Arguments:
* **iv** (*bytes*, *bytearray*, *memoryview*) --
(Only applicable for ``MODE_CBC``, ``MODE_CFB``, ``MODE_OFB``,
and ``MODE_OPENPGP`` modes).
The initialization vector to use for encryption or decryption.
For ``MODE_CBC``, ``MODE_CFB``, and ``MODE_OFB`` it must be 8 bytes long.
For ``MODE_OPENPGP`` mode only,
it 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).
If not provided, a random byte string is generated (you must then
read its value with the :attr:`iv` attribute).
* **nonce** (*bytes*, *bytearray*, *memoryview*) --
(Only applicable for ``MODE_EAX`` and ``MODE_CTR``).
A value that must never be reused for any other encryption done
with this key.
For ``MODE_EAX`` there are no
restrictions on its length (recommended: **16** bytes).
For ``MODE_CTR``, its length must be in the range **[0..7]**.
If not provided for ``MODE_EAX``, a random byte string is generated (you
can read it back via the ``nonce`` attribute).
* **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.
* **mac_len** : (*integer*) --
(Only ``MODE_EAX``)
Length of the authentication tag, in bytes.
It must be no longer than 8 (default).
* **initial_value** : (*integer*) --
(Only ``MODE_CTR``). The initial value for the counter within
the counter block. By default it is **0**.
:Return: a Triple DES object, of the applicable mode.
"""
return _create_cipher(sys.modules[__name__], key, mode, *args, **kwargs)
MODE_ECB = 1
MODE_CBC = 2
MODE_CFB = 3
MODE_OFB = 5
MODE_CTR = 6
MODE_OPENPGP = 7
MODE_EAX = 9
# Size of a data block (in bytes)
block_size = 8
# Size of a key (in bytes)
key_size = (16, 24)
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