121 lines
4.5 KiB
Python
121 lines
4.5 KiB
Python
# -*- coding: utf-8 -*-
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#
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# Cipher/Blowfish.py : Blowfish
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#
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# ===================================================================
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# The contents of this file are dedicated to the public domain. To
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# the extent that dedication to the public domain is not available,
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# everyone is granted a worldwide, perpetual, royalty-free,
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# non-exclusive license to exercise all rights associated with the
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# contents of this file for any purpose whatsoever.
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# No rights are reserved.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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# SOFTWARE.
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# ===================================================================
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"""Blowfish symmetric cipher
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Blowfish_ is a symmetric block cipher designed by Bruce Schneier.
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It has a fixed data block size of 8 bytes and its keys can vary in length
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from 32 to 448 bits (4 to 56 bytes).
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Blowfish is deemed secure and it is fast. However, its keys should be chosen
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to be big enough to withstand a brute force attack (e.g. at least 16 bytes).
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As an example, encryption can be done as follows:
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>>> from Crypto.Cipher import Blowfish
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>>> from Crypto import Random
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>>> from struct import pack
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>>>
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>>> bs = Blowfish.block_size
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>>> key = b'An arbitrarily long key'
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>>> iv = Random.new().read(bs)
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>>> cipher = Blowfish.new(key, Blowfish.MODE_CBC, iv)
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>>> plaintext = b'docendo discimus '
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>>> plen = bs - divmod(len(plaintext),bs)[1]
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>>> padding = [plen]*plen
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>>> padding = pack('b'*plen, *padding)
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>>> msg = iv + cipher.encrypt(plaintext + padding)
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.. _Blowfish: http://www.schneier.com/blowfish.html
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:undocumented: __revision__, __package__
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"""
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__revision__ = "$Id$"
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from Crypto.Cipher import blockalgo
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from Crypto.Cipher import _Blowfish
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class BlowfishCipher (blockalgo.BlockAlgo):
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"""Blowfish cipher object"""
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def __init__(self, key, *args, **kwargs):
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"""Initialize a Blowfish cipher object
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See also `new()` at the module level."""
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blockalgo.BlockAlgo.__init__(self, _Blowfish, key, *args, **kwargs)
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def new(key, *args, **kwargs):
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"""Create a new Blowfish cipher
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:Parameters:
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key : byte string
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The secret key to use in the symmetric cipher.
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Its length can vary from 4 to 56 bytes.
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:Keywords:
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mode : a *MODE_** constant
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The chaining mode to use for encryption or decryption.
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Default is `MODE_ECB`.
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IV : byte string
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The initialization vector to use for encryption or decryption.
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It is ignored for `MODE_ECB` and `MODE_CTR`.
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For `MODE_OPENPGP`, IV must be `block_size` bytes long for encryption
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and `block_size` +2 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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It is mandatory.
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For all other modes, it must be `block_size` bytes longs. It is optional and
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when not present it will be given a default value of all zeroes.
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counter : callable
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(*Only* `MODE_CTR`). A stateful function that returns the next
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*counter block*, which is a byte string of `block_size` bytes.
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For better performance, use `Crypto.Util.Counter`.
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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.
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It must be a multiple of 8. If 0 or not specified, it will be assumed to be 8.
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:Return: a `BlowfishCipher` object
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"""
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return BlowfishCipher(key, *args, **kwargs)
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#: Electronic Code Book (ECB). See `blockalgo.MODE_ECB`.
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MODE_ECB = 1
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#: Cipher-Block Chaining (CBC). See `blockalgo.MODE_CBC`.
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MODE_CBC = 2
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#: Cipher FeedBack (CFB). See `blockalgo.MODE_CFB`.
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MODE_CFB = 3
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#: This mode should not be used.
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MODE_PGP = 4
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#: Output FeedBack (OFB). See `blockalgo.MODE_OFB`.
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MODE_OFB = 5
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#: CounTer Mode (CTR). See `blockalgo.MODE_CTR`.
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MODE_CTR = 6
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#: OpenPGP Mode. See `blockalgo.MODE_OPENPGP`.
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MODE_OPENPGP = 7
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#: Size of a data block (in bytes)
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block_size = 8
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#: Size of a key (in bytes)
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key_size = range(4,56+1)
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