mirror of
https://github.com/Sneed-Group/Poodletooth-iLand
synced 2024-12-26 21:22:27 -06:00
133 lines
5 KiB
Python
133 lines
5 KiB
Python
# -*- 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
|
|
# SOFTWARE.
|
|
# ===================================================================
|
|
"""Triple DES symmetric cipher
|
|
|
|
`Triple DES`__ (or TDES or TDEA or 3DES) is a symmetric block cipher standardized by NIST_.
|
|
It has a fixed data block size of 8 bytes. Its keys are 128 (*Option 1*) or 192
|
|
bits (*Option 2*) long.
|
|
However, 1 out of 8 bits is used for redundancy and do not contribute to
|
|
security. The effective key length is respectively 112 or 168 bits.
|
|
|
|
TDES consists of the concatenation of 3 simple `DES` ciphers.
|
|
|
|
The plaintext is first DES encrypted with *K1*, then decrypted with *K2*,
|
|
and finally encrypted again with *K3*. The ciphertext is decrypted in the reverse manner.
|
|
|
|
The 192 bit key is a bundle of three 64 bit independent subkeys: *K1*, *K2*, and *K3*.
|
|
|
|
The 128 bit key is split into *K1* and *K2*, whereas *K1=K3*.
|
|
|
|
It is important that all subkeys are different, otherwise TDES would degrade to
|
|
single `DES`.
|
|
|
|
TDES is cryptographically secure, even though it is neither as secure nor as fast
|
|
as `AES`.
|
|
|
|
As an example, encryption can be done as follows:
|
|
|
|
>>> from Crypto.Cipher import DES
|
|
>>> from Crypto import Random
|
|
>>> from Crypto.Util import Counter
|
|
>>>
|
|
>>> key = b'-8B key-'
|
|
>>> nonce = Random.new().read(DES.block_size/2)
|
|
>>> ctr = Counter.new(DES.block_size*8/2, prefix=nonce)
|
|
>>> cipher = DES.new(key, DES.MODE_CTR, counter=ctr)
|
|
>>> plaintext = b'We are no longer the knights who say ni!'
|
|
>>> msg = nonce + cipher.encrypt(plaintext)
|
|
|
|
.. __: http://en.wikipedia.org/wiki/Triple_DES
|
|
.. _NIST: http://csrc.nist.gov/publications/nistpubs/800-67/SP800-67.pdf
|
|
|
|
:undocumented: __revision__, __package__
|
|
"""
|
|
|
|
__revision__ = "$Id$"
|
|
|
|
from Crypto.Cipher import blockalgo
|
|
from Crypto.Cipher import _DES3
|
|
|
|
class DES3Cipher(blockalgo.BlockAlgo):
|
|
"""TDES cipher object"""
|
|
|
|
def __init__(self, key, *args, **kwargs):
|
|
"""Initialize a TDES cipher object
|
|
|
|
See also `new()` at the module level."""
|
|
blockalgo.BlockAlgo.__init__(self, _DES3, key, *args, **kwargs)
|
|
|
|
def new(key, *args, **kwargs):
|
|
"""Create a new TDES cipher
|
|
|
|
:Parameters:
|
|
key : byte string
|
|
The secret key to use in the symmetric cipher.
|
|
It must be 16 or 24 bytes long. The parity bits will be ignored.
|
|
:Keywords:
|
|
mode : a *MODE_** constant
|
|
The chaining mode to use for encryption or decryption.
|
|
Default is `MODE_ECB`.
|
|
IV : byte string
|
|
The initialization vector to use for encryption or decryption.
|
|
|
|
It is ignored for `MODE_ECB` and `MODE_CTR`.
|
|
|
|
For `MODE_OPENPGP`, IV must be `block_size` bytes long for encryption
|
|
and `block_size` +2 bytes for decryption (in the latter case, it is
|
|
actually the *encrypted* IV which was prefixed to the ciphertext).
|
|
It is mandatory.
|
|
|
|
For all other modes, it must be `block_size` bytes longs. It is optional and
|
|
when not present it will be given a default value of all zeroes.
|
|
counter : callable
|
|
(*Only* `MODE_CTR`). A stateful function that returns the next
|
|
*counter block*, which is a byte string of `block_size` bytes.
|
|
For better performance, use `Crypto.Util.Counter`.
|
|
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 0 or not specified, it will be assumed to be 8.
|
|
|
|
:Attention: it is important that all 8 byte subkeys are different,
|
|
otherwise TDES would degrade to single `DES`.
|
|
:Return: an `DES3Cipher` object
|
|
"""
|
|
return DES3Cipher(key, *args, **kwargs)
|
|
|
|
#: Electronic Code Book (ECB). See `blockalgo.MODE_ECB`.
|
|
MODE_ECB = 1
|
|
#: Cipher-Block Chaining (CBC). See `blockalgo.MODE_CBC`.
|
|
MODE_CBC = 2
|
|
#: Cipher FeedBack (CFB). See `blockalgo.MODE_CFB`.
|
|
MODE_CFB = 3
|
|
#: This mode should not be used.
|
|
MODE_PGP = 4
|
|
#: Output FeedBack (OFB). See `blockalgo.MODE_OFB`.
|
|
MODE_OFB = 5
|
|
#: CounTer Mode (CTR). See `blockalgo.MODE_CTR`.
|
|
MODE_CTR = 6
|
|
#: OpenPGP Mode. See `blockalgo.MODE_OPENPGP`.
|
|
MODE_OPENPGP = 7
|
|
#: Size of a data block (in bytes)
|
|
block_size = 8
|
|
#: Size of a key (in bytes)
|
|
key_size = ( 16, 24 )
|