Added documentation for Triple DES.

4 files changed, 114 insertions, 2 deletions

diff --git a/lib/Crypto/Cipher/DES.py b/lib/Crypto/Cipher/DES.py
index 24a19b3..3b981d3 100644
--- a/lib/Crypto/Cipher/DES.py
+++ b/lib/Crypto/Cipher/DES.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 #
 #  Cipher/DES.py : DES
 #
diff --git a/lib/Crypto/Cipher/DES3.py b/lib/Crypto/Cipher/DES3.py
new file mode 100644
index 0000000..642cb7a
--- /dev/null
+++ b/lib/Crypto/Cipher/DES3.py
@@ -0,0 +1,111 @@
+# -*- 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`.
+
+.. __: 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 blockalgo import *
+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, _DES, 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 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.
+
+    :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
+#: Size of a data block (in bytes)
+block_size = 8
+#: Size of a key (in bytes)
+key_size = { 16, 24 }
diff --git a/setup.py b/setup.py
index 8a22b6e..73e7780 100644
--- a/setup.py
+++ b/setup.py
@@ -410,7 +410,7 @@ kw = {'name':"pycrypto",
             Extension("Crypto.Cipher._DES",
                       include_dirs=['src/', 'src/libtom/'],
                       sources=["src/DES.c"]),
-            Extension("Crypto.Cipher.DES3",
+            Extension("Crypto.Cipher._DES3",
                       include_dirs=['src/', 'src/libtom/'],
                       sources=["src/DES3.c"]),
 
diff --git a/src/DES.c b/src/DES.c
index ba63a09..96a9335 100644
--- a/src/DES.c
+++ b/src/DES.c
@@ -98,7 +98,7 @@ static void block_decrypt(block_state *self, unsigned char *in, unsigned char *o
 }
 
 #ifdef PCT_DES3_MODULE
-# define MODULE_NAME DES3   /* triple DES */
+# define MODULE_NAME _DES3   /* triple DES */
 # define BLOCK_SIZE 8       /* 64-bit block size */
 # define KEY_SIZE  0        /* variable key size (can be 128 or 192 bits (including parity) */
 #else