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Diffstat (limited to 'frozen_deps/Crypto/Cipher/CAST.py')
| -rw-r--r-- | frozen_deps/Crypto/Cipher/CAST.py | 123 |
1 files changed, 123 insertions, 0 deletions
diff --git a/frozen_deps/Crypto/Cipher/CAST.py b/frozen_deps/Crypto/Cipher/CAST.py new file mode 100644 index 0000000..89543b2 --- /dev/null +++ b/frozen_deps/Crypto/Cipher/CAST.py @@ -0,0 +1,123 @@ +# -*- 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. +# =================================================================== +"""CAST-128 symmetric cipher + +CAST-128_ (or CAST5) is a symmetric block cipher specified in RFC2144_. + +It has a fixed data block size of 8 bytes. Its key can vary in length +from 40 to 128 bits. + +CAST is deemed to be cryptographically secure, but its usage is not widespread. +Keys of sufficient length should be used to prevent brute force attacks +(128 bits are recommended). + +As an example, encryption can be done as follows: + + >>> from Crypto.Cipher import CAST + >>> from Crypto import Random + >>> + >>> key = b'Sixteen byte key' + >>> iv = Random.new().read(CAST.block_size) + >>> cipher = CAST.new(key, CAST.MODE_OPENPGP, iv) + >>> plaintext = b'sona si latine loqueris ' + >>> msg = cipher.encrypt(plaintext) + >>> + ... + >>> eiv = msg[:CAST.block_size+2] + >>> ciphertext = msg[CAST.block_size+2:] + >>> cipher = CAST.new(key, CAST.MODE_OPENPGP, eiv) + >>> print cipher.decrypt(ciphertext) + +.. _CAST-128: http://en.wikipedia.org/wiki/CAST-128 +.. _RFC2144: http://tools.ietf.org/html/rfc2144 + +:undocumented: __revision__, __package__ +""" + +__revision__ = "$Id$" + +from Crypto.Cipher import blockalgo +from Crypto.Cipher import _CAST + +class CAST128Cipher(blockalgo.BlockAlgo): + """CAST-128 cipher object""" + + def __init__(self, key, *args, **kwargs): + """Initialize a CAST-128 cipher object + + See also `new()` at the module level.""" + blockalgo.BlockAlgo.__init__(self, _CAST, key, *args, **kwargs) + +def new(key, *args, **kwargs): + """Create a new CAST-128 cipher + + :Parameters: + key : byte string + The secret key to use in the symmetric cipher. + Its length may vary from 5 to 16 bytes. + :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. + + :Return: an `CAST128Cipher` object + """ + return CAST128Cipher(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 = range(5,16+1) |