Added documentation for Blowfish

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diff --git a/lib/Crypto/Cipher/Blowfish.py b/lib/Crypto/Cipher/Blowfish.py
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+# -*- coding: utf-8 -*-
+#
+#  Cipher/Blowfish.py : Blowfish
+#
+# ===================================================================
+# 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.
+# ===================================================================
+"""Blowfish symmetric cipher
+
+Blowfish_ is a symmetric block cipher designed by Bruce Schneier.
+
+It has a fixed data block size of 8 bytes and its keys can vary in length
+from 32 to 448 bits (4 to 56 bytes).
+
+Blowfish is deemed secure and it is fast. However, its keys should be chosen
+to be big enough to withstand a brute force attack (e.g. at least 16 bytes).
+
+.. _Blowfish: http://www.schneier.com/blowfish.html
+
+:undocumented: __revision__, __package__
+"""
+
+__revision__ = "$Id$"
+
+from Crypto.Cipher import blockalgo
+from blockalgo import *
+from Crypto.Cipher import _Blowfish
+
+class BlowfishCipher (blockalgo.BlockAlgo):
+    """Blowfish cipher object"""
+
+    def __init__(self, key, *args, **kwargs):
+        """Initialize a Blowfish cipher object
+        
+        See also `new()` at the module level."""
+        blockalgo.BlockAlgo.__init__(self, _Blowfish, key, *args, **kwargs)
+
+def new(key, *args, **kwargs):
+    """Create a new Blowfish cipher
+
+    :Parameters:
+      key : byte string
+        The secret key to use in the symmetric cipher.
+        Its length can vary from 4 to 56 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 must be `block_size` bytes longs. Ignored for `MODE_ECB`
+        and `MODE_CTR`. The default value is 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: a `BlowfishCipher` object
+    """
+    return BlowfishCipher(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
+#: Size of a data block (in bytes)
+block_size = 8
+#: Size of a key (in bytes)
+key_size = xrange(4,56)
+