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Editing: CAST.py
# -*- coding: utf-8 -*- # # Cipher/CAST.py : CAST # # =================================================================== # 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 CAST: :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_cast_lib = load_pycryptodome_raw_lib( "Crypto.Cipher._raw_cast", """ int CAST_start_operation(const uint8_t key[], size_t key_len, void **pResult); int CAST_encrypt(const void *state, const uint8_t *in, uint8_t *out, size_t data_len); int CAST_decrypt(const void *state, const uint8_t *in, uint8_t *out, size_t data_len); int CAST_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") if len(key) not in key_size: raise ValueError("Incorrect CAST key length (%d bytes)" % len(key)) start_operation = _raw_cast_lib.CAST_start_operation stop_operation = _raw_cast_lib.CAST_stop_operation cipher = VoidPointer() result = start_operation(c_uint8_ptr(key), c_size_t(len(key)), cipher.address_of()) if result: raise ValueError("Error %X while instantiating the CAST cipher" % result) return SmartPointer(cipher.get(), stop_operation) def new(key, mode, *args, **kwargs): """Create a new CAST cipher :param key: The secret key to use in the symmetric cipher. Its length can vary from 5 to 16 bytes. :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 CAST 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, 16 + 1)
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