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# -*- coding: utf-8 -*-
#
# Cipher/ARC2.py : ARC2.py
#
# ===================================================================
# 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.
# ===================================================================
"""
Module's constants for the modes of operation supported with ARC2:
: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
from Crypto.Util._raw_api import (load_pycryptodome_raw_lib,
VoidPointer, SmartPointer,
c_size_t, c_uint8_ptr)
_raw_arc2_lib = load_pycryptodome_raw_lib(
"Crypto.Cipher._raw_arc2",
"""
int ARC2_start_operation(const uint8_t key[],
size_t key_len,
size_t effective_key_len,
void **pResult);
int ARC2_encrypt(const void *state,
const uint8_t *in,
uint8_t *out,
size_t data_len);
int ARC2_decrypt(const void *state,
const uint8_t *in,
uint8_t *out,
size_t data_len);
int ARC2_stop_operation(void *state);
"""
)
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 = dict_parameters.pop("key")
except KeyError:
raise TypeError("Missing 'key' parameter")
effective_keylen = dict_parameters.pop("effective_keylen", 1024)
if len(key) not in key_size:
raise ValueError("Incorrect ARC2 key length (%d bytes)" % len(key))
if not (40 <= effective_keylen <= 1024):
raise ValueError("'effective_key_len' must be at least 40 and no larger than 1024 "
"(not %d)" % effective_keylen)
start_operation = _raw_arc2_lib.ARC2_start_operation
stop_operation = _raw_arc2_lib.ARC2_stop_operation
cipher = VoidPointer()
result = start_operation(c_uint8_ptr(key),
c_size_t(len(key)),
c_size_t(effective_keylen),
cipher.address_of())
if result:
raise ValueError("Error %X while instantiating the ARC2 cipher"
% result)
return SmartPointer(cipher.get(), stop_operation)
def new(key, mode, *args, **kwargs):
"""Create a new RC2 cipher.
:param key:
The secret key to use in the symmetric cipher.
Its length can vary from 5 to 128 bytes; the actual search space
(and the cipher strength) can be reduced with the ``effective_keylen`` parameter.
: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).
* **effective_keylen** (*integer*) --
Optional. Maximum strength in bits of the actual key used by the ARC2 algorithm.
If the supplied ``key`` parameter is longer (in bits) of the value specified
here, it will be weakened to match it.
If not specified, no limitation is applied.
* **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: an ARC2 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 = range(5, 128 + 1)