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| """
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| Module's constants for the modes of operation supported with ARC2:
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| :var MODE_ECB: :ref:`Electronic Code Book (ECB) <ecb_mode>`
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| :var MODE_CBC: :ref:`Cipher-Block Chaining (CBC) <cbc_mode>`
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| :var MODE_CFB: :ref:`Cipher FeedBack (CFB) <cfb_mode>`
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| :var MODE_OFB: :ref:`Output FeedBack (OFB) <ofb_mode>`
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| :var MODE_CTR: :ref:`CounTer Mode (CTR) <ctr_mode>`
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| :var MODE_OPENPGP: :ref:`OpenPGP Mode <openpgp_mode>`
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| :var MODE_EAX: :ref:`EAX Mode <eax_mode>`
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| """
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|
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| import sys
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|
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| from Cryptodome.Cipher import _create_cipher
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| from Cryptodome.Util.py3compat import byte_string
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| from Cryptodome.Util._raw_api import (load_pycryptodome_raw_lib,
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| VoidPointer, SmartPointer,
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| c_size_t, c_uint8_ptr)
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| _raw_arc2_lib = load_pycryptodome_raw_lib(
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| "Cryptodome.Cipher._raw_arc2",
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| """
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| int ARC2_start_operation(const uint8_t key[],
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| size_t key_len,
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| size_t effective_key_len,
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| void **pResult);
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| int ARC2_encrypt(const void *state,
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| const uint8_t *in,
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| uint8_t *out,
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| size_t data_len);
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| int ARC2_decrypt(const void *state,
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| const uint8_t *in,
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| uint8_t *out,
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| size_t data_len);
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| int ARC2_stop_operation(void *state);
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| """
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| )
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| def _create_base_cipher(dict_parameters):
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| """This method instantiates and returns a handle to a low-level
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| base cipher. It will absorb named parameters in the process."""
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| try:
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| key = dict_parameters.pop("key")
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| except KeyError:
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| raise TypeError("Missing 'key' parameter")
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| effective_keylen = dict_parameters.pop("effective_keylen", 1024)
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| if len(key) not in key_size:
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| raise ValueError("Incorrect ARC2 key length (%d bytes)" % len(key))
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| if not (40 <= effective_keylen <= 1024):
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| raise ValueError("'effective_key_len' must be at least 40 and no larger than 1024 "
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| "(not %d)" % effective_keylen)
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| start_operation = _raw_arc2_lib.ARC2_start_operation
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| stop_operation = _raw_arc2_lib.ARC2_stop_operation
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| cipher = VoidPointer()
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| result = start_operation(c_uint8_ptr(key),
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| c_size_t(len(key)),
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| c_size_t(effective_keylen),
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| cipher.address_of())
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| if result:
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| raise ValueError("Error %X while instantiating the ARC2 cipher"
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| % result)
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| return SmartPointer(cipher.get(), stop_operation)
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| def new(key, mode, *args, **kwargs):
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| """Create a new RC2 cipher.
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| :param key:
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| The secret key to use in the symmetric cipher.
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| Its length can vary from 5 to 128 bytes; the actual search space
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| (and the cipher strength) can be reduced with the ``effective_keylen`` parameter.
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| :type key: bytes, bytearray, memoryview
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| :param mode:
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| The chaining mode to use for encryption or decryption.
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| :type mode: One of the supported ``MODE_*`` constants
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| :Keyword Arguments:
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| * **iv** (*bytes*, *bytearray*, *memoryview*) --
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| (Only applicable for ``MODE_CBC``, ``MODE_CFB``, ``MODE_OFB``,
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| and ``MODE_OPENPGP`` modes).
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| The initialization vector to use for encryption or decryption.
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| For ``MODE_CBC``, ``MODE_CFB``, and ``MODE_OFB`` it must be 8 bytes long.
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| For ``MODE_OPENPGP`` mode only,
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| it must be 8 bytes long for encryption
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| and 10 bytes for decryption (in the latter case, it is
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| actually the *encrypted* IV which was prefixed to the ciphertext).
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| If not provided, a random byte string is generated (you must then
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| read its value with the :attr:`iv` attribute).
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| * **nonce** (*bytes*, *bytearray*, *memoryview*) --
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| (Only applicable for ``MODE_EAX`` and ``MODE_CTR``).
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| A value that must never be reused for any other encryption done
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| with this key.
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| For ``MODE_EAX`` there are no
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| restrictions on its length (recommended: **16** bytes).
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|
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| For ``MODE_CTR``, its length must be in the range **[0..7]**.
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| If not provided for ``MODE_EAX``, a random byte string is generated (you
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| can read it back via the ``nonce`` attribute).
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|
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| * **effective_keylen** (*integer*) --
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| Optional. Maximum strength in bits of the actual key used by the ARC2 algorithm.
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| If the supplied ``key`` parameter is longer (in bits) of the value specified
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| here, it will be weakened to match it.
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| If not specified, no limitation is applied.
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| * **segment_size** (*integer*) --
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| (Only ``MODE_CFB``).The number of **bits** the plaintext and ciphertext
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| are segmented in. It must be a multiple of 8.
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| If not specified, it will be assumed to be 8.
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| * **mac_len** : (*integer*) --
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| (Only ``MODE_EAX``)
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| Length of the authentication tag, in bytes.
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| It must be no longer than 8 (default).
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|
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| * **initial_value** : (*integer*) --
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| (Only ``MODE_CTR``). The initial value for the counter within
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| the counter block. By default it is **0**.
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|
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| :Return: an ARC2 object, of the applicable mode.
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| """
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|
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| return _create_cipher(sys.modules[__name__], key, mode, *args, **kwargs)
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|
|
| MODE_ECB = 1
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| MODE_CBC = 2
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| MODE_CFB = 3
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| MODE_OFB = 5
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| MODE_CTR = 6
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| MODE_OPENPGP = 7
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| MODE_EAX = 9
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| block_size = 8
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|
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| key_size = range(5, 128 + 1)
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|
|
