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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 |
| |
|
| | |
| | block_size = 8 |
| | |
| | key_size = (16, 24) |
| |
|
