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diff --git a/lib/Crypto/Cipher/_mode_openpgp.py b/lib/Crypto/Cipher/_mode_openpgp.py
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+++ b/lib/Crypto/Cipher/_mode_openpgp.py
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+# ===================================================================
+#
+# Copyright (c) 2014, Legrandin <helderijs@gmail.com>
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+# COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+# ===================================================================
+
+"""
+OpenPGP mode.
+"""
+
+__all__ = ['OpenPgpMode']
+
+from Crypto.Util.py3compat import _copy_bytes
+from Crypto.Random import get_random_bytes
+
+class OpenPgpMode(object):
+    """OpenPGP mode.
+
+    This mode is a variant of CFB, and it is only used in PGP and
+    OpenPGP_ applications. If in doubt, use another mode.
+
+    An Initialization Vector (*IV*) is required.
+
+    Unlike CFB, the *encrypted* IV (not the IV itself) is
+    transmitted to the receiver.
+
+    The IV is a random data block. For legacy reasons, two of its bytes are
+    duplicated to act as a checksum for the correctness of the key, which is now
+    known to be insecure and is ignored. The encrypted IV is therefore 2 bytes
+    longer than the clean IV.
+
+    .. _OpenPGP: http://tools.ietf.org/html/rfc4880
+
+    :undocumented: __init__
+    """
+
+    def __init__(self, factory, key, iv, cipher_params):
+
+        #: The block size of the underlying cipher, in bytes.
+        self.block_size = factory.block_size
+
+        self._done_first_block = False  # True after the first encryption
+
+        # Instantiate a temporary cipher to process the IV
+        IV_cipher = factory.new(
+                        key,
+                        factory.MODE_CFB,
+                        IV=b'\x00' * self.block_size,
+                        segment_size=self.block_size * 8,
+                        **cipher_params)
+
+        iv = _copy_bytes(None, None, iv)
+
+        # The cipher will be used for...
+        if len(iv) == self.block_size:
+            # ... encryption
+            self._encrypted_IV = IV_cipher.encrypt(iv + iv[-2:])
+        elif len(iv) == self.block_size + 2:
+            # ... decryption
+            self._encrypted_IV = iv
+            # Last two bytes are for a deprecated "quick check" feature that
+            # should not be used. (https://eprint.iacr.org/2005/033)
+            iv = IV_cipher.decrypt(iv)[:-2]
+        else:
+            raise ValueError("Length of IV must be %d or %d bytes"
+                             " for MODE_OPENPGP"
+                             % (self.block_size, self.block_size + 2))
+
+        self.iv = self.IV = iv
+
+        # Instantiate the cipher for the real PGP data
+        self._cipher = factory.new(
+                            key,
+                            factory.MODE_CFB,
+                            IV=self._encrypted_IV[-self.block_size:],
+                            segment_size=self.block_size * 8,
+                            **cipher_params)
+
+    def encrypt(self, plaintext):
+        """Encrypt data with the key and the parameters set at initialization.
+
+        A cipher object is stateful: once you have encrypted a message
+        you cannot encrypt (or decrypt) another message using the same
+        object.
+
+        The data to encrypt can be broken up in two or
+        more pieces and `encrypt` can be called multiple times.
+
+        That is, the statement:
+
+            >>> c.encrypt(a) + c.encrypt(b)
+
+        is equivalent to:
+
+             >>> c.encrypt(a+b)
+
+        This function does not add any padding to the plaintext.
+
+        :Parameters:
+          plaintext : bytes/bytearray/memoryview
+            The piece of data to encrypt.
+
+        :Return:
+            the encrypted data, as a byte string.
+            It is as long as *plaintext* with one exception:
+            when encrypting the first message chunk,
+            the encypted IV is prepended to the returned ciphertext.
+        """
+
+        res = self._cipher.encrypt(plaintext)
+        if not self._done_first_block:
+            res = self._encrypted_IV + res
+            self._done_first_block = True
+        return res
+
+    def decrypt(self, ciphertext):
+        """Decrypt data with the key and the parameters set at initialization.
+
+        A cipher object is stateful: once you have decrypted a message
+        you cannot decrypt (or encrypt) another message with the same
+        object.
+
+        The data to decrypt can be broken up in two or
+        more pieces and `decrypt` can be called multiple times.
+
+        That is, the statement:
+
+            >>> c.decrypt(a) + c.decrypt(b)
+
+        is equivalent to:
+
+             >>> c.decrypt(a+b)
+
+        This function does not remove any padding from the plaintext.
+
+        :Parameters:
+          ciphertext : bytes/bytearray/memoryview
+            The piece of data to decrypt.
+
+        :Return: the decrypted data (byte string).
+        """
+
+        return self._cipher.decrypt(ciphertext)
+
+
+def _create_openpgp_cipher(factory, **kwargs):
+    """Create a new block cipher, configured in OpenPGP mode.
+
+    :Parameters:
+      factory : module
+        The module.
+
+    :Keywords:
+      key : bytes/bytearray/memoryview
+        The secret key to use in the symmetric cipher.
+
+      IV : bytes/bytearray/memoryview
+        The initialization vector to use for encryption or decryption.
+
+        For encryption, the IV must be as long as the cipher block size.
+
+        For decryption, it must be 2 bytes longer (it is actually the
+        *encrypted* IV which was prefixed to the ciphertext).
+    """
+
+    iv = kwargs.pop("IV", None)
+    IV = kwargs.pop("iv", None)
+
+    if (None, None) == (iv, IV):
+        iv = get_random_bytes(factory.block_size)
+    if iv is not None:
+        if IV is not None:
+            raise TypeError("You must either use 'iv' or 'IV', not both")
+    else:
+        iv = IV
+
+    try:
+        key = kwargs.pop("key")
+    except KeyError as e:
+        raise TypeError("Missing component: " + str(e))
+
+    return OpenPgpMode(factory, key, iv, kwargs)