diff options
-rw-r--r-- | lib/Crypto/Cipher/ARC4.py | 108 | ||||
-rw-r--r-- | setup.py | 2 | ||||
-rw-r--r-- | src/ARC4.c | 2 |
3 files changed, 110 insertions, 2 deletions
diff --git a/lib/Crypto/Cipher/ARC4.py b/lib/Crypto/Cipher/ARC4.py new file mode 100644 index 0000000..de5e4e8 --- /dev/null +++ b/lib/Crypto/Cipher/ARC4.py @@ -0,0 +1,108 @@ +# -*- coding: utf-8 -*- +# +# Cipher/ARC4.py : ARC4 +# +# =================================================================== +# 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. +# =================================================================== +"""ARC4 symmetric cipher + +ARC4_ (Alleged RC4) is an implementation of RC4 (Rivest's Cipher version 4), +a symmetric stream cipher designed by Ron Rivest in 1987. + +The cipher started as a proprietary design, that was reverse engineered and +anonymously posted on Usenet in 1994. The company that owns RC4 (RSA Data +Inc.) never confirmed the correctness of the leaked algorithm. + +Unlike RC2, the company has never published the full specification of RC4, +of whom it still holds the trademark. + +ARC4 keys can vary in length from 40 to 2048 bits. + +One problem of ARC4 is that it does not take a nonce or an IV. If it is required +to encrypt multiple messages with the same long-term key, a distinct +independent nonce must be created for each message, and a short-term key must +be derived from the combination of the long-term key and the nonce. +Due to the weak key scheduling algorithm of RC2, the combination must be carried +out with a complex function (e.g. a cryptographic hash) and not by simply +concatenating key and nonce. + +New designs should not use ARC4. A good alternative is AES +(`Crypto.Cipher.AES`) in any of the modes that turn it into a stream cipher (OFB, CFB, or CTR). + +.. _ARC4: http://en.wikipedia.org/wiki/RC4 + +:undocumented: __revision__, __package__ +""" + +__revision__ = "$Id$" + +from Crypto.Cipher import _ARC4 + +class ARC4Cipher: + """ARC4 cipher object""" + + + def __init__(self, key, *args, **kwargs): + """Initialize an ARC4 cipher object + + See also `new()` at the module level.""" + + self._cipher = _ARC4.new(key, *args, **kwargs) + self.block_size = self._cipher.block_size + self.key_size = self._cipher.key_size + + def encrypt(self, plaintext): + """Encrypt a piece of data. + + :Parameters: + plaintext : byte string + The piece of data to encrypt. It can be of any size. + :Return: the encrypted data (byte string, as long as the + plaintext). + """ + return self._cipher.encrypt(plaintext) + + def decrypt(self, ciphertext): + """Decrypt a piece of data. + + :Parameters: + ciphertext : byte string + The piece of data to decrypt. It can be of any size. + :Return: the decrypted data (byte string, as long as the + ciphertext). + """ + return self._cipher.decrypt(ciphertext) + +def new(key, *args, **kwargs): + """Create a new ARC4 cipher + + :Parameters: + key : byte string + The secret key to use in the symmetric cipher. + It can have any length, with a minimum of 40 bytes. + Its cryptograpic strength is always capped to 2048 bits (256 bytes). + + :Return: an `ARC4Cipher` object + """ + return ARC4Cipher(key, *args, **kwargs) + +#: Size of a data block (in bytes) +block_size = 1 +#: Size of a key (in bytes) +key_size = xrange(1,256+1) + @@ -415,7 +415,7 @@ kw = {'name':"pycrypto", sources=["src/DES3.c"]), # Stream ciphers - Extension("Crypto.Cipher.ARC4", + Extension("Crypto.Cipher._ARC4", include_dirs=['src/'], sources=["src/ARC4.c"]), Extension("Crypto.Cipher.XOR", @@ -26,7 +26,7 @@ * */ -#define MODULE_NAME ARC4 +#define MODULE_NAME _ARC4 #define BLOCK_SIZE 1 #define KEY_SIZE 0 |