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https://github.com/Sneed-Group/Poodletooth-iLand
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255 lines
9.2 KiB
Python
255 lines
9.2 KiB
Python
# -*- coding: utf-8 -*-
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#
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# Cipher/PKCS1_OAEP.py : PKCS#1 OAEP
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#
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# ===================================================================
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# The contents of this file are dedicated to the public domain. To
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# the extent that dedication to the public domain is not available,
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# everyone is granted a worldwide, perpetual, royalty-free,
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# non-exclusive license to exercise all rights associated with the
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# contents of this file for any purpose whatsoever.
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# No rights are reserved.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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# SOFTWARE.
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# ===================================================================
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"""RSA encryption protocol according to PKCS#1 OAEP
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See RFC3447__ or the `original RSA Labs specification`__ .
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This scheme is more properly called ``RSAES-OAEP``.
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As an example, a sender may encrypt a message in this way:
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>>> from Crypto.Cipher import PKCS1_OAEP
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>>> from Crypto.PublicKey import RSA
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>>>
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>>> message = 'To be encrypted'
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>>> key = RSA.importKey(open('pubkey.der').read())
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>>> cipher = PKCS1_OAEP.new(key)
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>>> ciphertext = cipher.encrypt(message)
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At the receiver side, decryption can be done using the private part of
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the RSA key:
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>>> key = RSA.importKey(open('privkey.der').read())
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>>> cipher = PKCS1_OAP.new(key)
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>>> message = cipher.decrypt(ciphertext)
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:undocumented: __revision__, __package__
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.. __: http://www.ietf.org/rfc/rfc3447.txt
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.. __: http://www.rsa.com/rsalabs/node.asp?id=2125.
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"""
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from __future__ import nested_scopes
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__revision__ = "$Id$"
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__all__ = [ 'new', 'PKCS1OAEP_Cipher' ]
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import Crypto.Signature.PKCS1_PSS
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import Crypto.Hash.SHA
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from Crypto.Util.py3compat import *
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import Crypto.Util.number
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from Crypto.Util.number import ceil_div
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from Crypto.Util.strxor import strxor
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class PKCS1OAEP_Cipher:
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"""This cipher can perform PKCS#1 v1.5 OAEP encryption or decryption."""
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def __init__(self, key, hashAlgo, mgfunc, label):
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"""Initialize this PKCS#1 OAEP cipher object.
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:Parameters:
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key : an RSA key object
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If a private half is given, both encryption and decryption are possible.
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If a public half is given, only encryption is possible.
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hashAlgo : hash object
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The hash function to use. This can be a module under `Crypto.Hash`
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or an existing hash object created from any of such modules. If not specified,
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`Crypto.Hash.SHA` (that is, SHA-1) is used.
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mgfunc : callable
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A mask generation function that accepts two parameters: a string to
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use as seed, and the lenth of the mask to generate, in bytes.
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If not specified, the standard MGF1 is used (a safe choice).
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label : string
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A label to apply to this particular encryption. If not specified,
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an empty string is used. Specifying a label does not improve
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security.
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:attention: Modify the mask generation function only if you know what you are doing.
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Sender and receiver must use the same one.
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"""
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self._key = key
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if hashAlgo:
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self._hashObj = hashAlgo
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else:
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self._hashObj = Crypto.Hash.SHA
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if mgfunc:
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self._mgf = mgfunc
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else:
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self._mgf = lambda x,y: Crypto.Signature.PKCS1_PSS.MGF1(x,y,self._hashObj)
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self._label = label
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def can_encrypt(self):
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"""Return True/1 if this cipher object can be used for encryption."""
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return self._key.can_encrypt()
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def can_decrypt(self):
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"""Return True/1 if this cipher object can be used for decryption."""
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return self._key.can_decrypt()
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def encrypt(self, message):
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"""Produce the PKCS#1 OAEP encryption of a message.
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This function is named ``RSAES-OAEP-ENCRYPT``, and is specified in
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section 7.1.1 of RFC3447.
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:Parameters:
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message : string
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The message to encrypt, also known as plaintext. It can be of
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variable length, but not longer than the RSA modulus (in bytes)
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minus 2, minus twice the hash output size.
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:Return: A string, the ciphertext in which the message is encrypted.
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It is as long as the RSA modulus (in bytes).
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:Raise ValueError:
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If the RSA key length is not sufficiently long to deal with the given
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message.
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"""
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# TODO: Verify the key is RSA
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randFunc = self._key._randfunc
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# See 7.1.1 in RFC3447
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modBits = Crypto.Util.number.size(self._key.n)
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k = ceil_div(modBits,8) # Convert from bits to bytes
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hLen = self._hashObj.digest_size
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mLen = len(message)
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# Step 1b
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ps_len = k-mLen-2*hLen-2
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if ps_len<0:
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raise ValueError("Plaintext is too long.")
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# Step 2a
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lHash = self._hashObj.new(self._label).digest()
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# Step 2b
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ps = bchr(0x00)*ps_len
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# Step 2c
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db = lHash + ps + bchr(0x01) + message
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# Step 2d
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ros = randFunc(hLen)
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# Step 2e
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dbMask = self._mgf(ros, k-hLen-1)
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# Step 2f
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maskedDB = strxor(db, dbMask)
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# Step 2g
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seedMask = self._mgf(maskedDB, hLen)
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# Step 2h
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maskedSeed = strxor(ros, seedMask)
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# Step 2i
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em = bchr(0x00) + maskedSeed + maskedDB
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# Step 3a (OS2IP), step 3b (RSAEP), part of step 3c (I2OSP)
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m = self._key.encrypt(em, 0)[0]
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# Complete step 3c (I2OSP)
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c = bchr(0x00)*(k-len(m)) + m
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return c
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def decrypt(self, ct):
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"""Decrypt a PKCS#1 OAEP ciphertext.
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This function is named ``RSAES-OAEP-DECRYPT``, and is specified in
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section 7.1.2 of RFC3447.
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:Parameters:
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ct : string
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The ciphertext that contains the message to recover.
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:Return: A string, the original message.
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:Raise ValueError:
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If the ciphertext length is incorrect, or if the decryption does not
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succeed.
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:Raise TypeError:
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If the RSA key has no private half.
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"""
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# TODO: Verify the key is RSA
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# See 7.1.2 in RFC3447
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modBits = Crypto.Util.number.size(self._key.n)
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k = ceil_div(modBits,8) # Convert from bits to bytes
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hLen = self._hashObj.digest_size
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# Step 1b and 1c
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if len(ct) != k or k<hLen+2:
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raise ValueError("Ciphertext with incorrect length.")
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# Step 2a (O2SIP), 2b (RSADP), and part of 2c (I2OSP)
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m = self._key.decrypt(ct)
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# Complete step 2c (I2OSP)
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em = bchr(0x00)*(k-len(m)) + m
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# Step 3a
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lHash = self._hashObj.new(self._label).digest()
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# Step 3b
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y = em[0]
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# y must be 0, but we MUST NOT check it here in order not to
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# allow attacks like Manger's (http://dl.acm.org/citation.cfm?id=704143)
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maskedSeed = em[1:hLen+1]
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maskedDB = em[hLen+1:]
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# Step 3c
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seedMask = self._mgf(maskedDB, hLen)
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# Step 3d
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seed = strxor(maskedSeed, seedMask)
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# Step 3e
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dbMask = self._mgf(seed, k-hLen-1)
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# Step 3f
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db = strxor(maskedDB, dbMask)
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# Step 3g
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valid = 1
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one = db[hLen:].find(bchr(0x01))
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lHash1 = db[:hLen]
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if lHash1!=lHash:
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valid = 0
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if one<0:
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valid = 0
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if bord(y)!=0:
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valid = 0
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if not valid:
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raise ValueError("Incorrect decryption.")
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# Step 4
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return db[hLen+one+1:]
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def new(key, hashAlgo=None, mgfunc=None, label=b('')):
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"""Return a cipher object `PKCS1OAEP_Cipher` that can be used to perform PKCS#1 OAEP encryption or decryption.
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:Parameters:
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key : RSA key object
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The key to use to encrypt or decrypt the message. This is a `Crypto.PublicKey.RSA` object.
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Decryption is only possible if *key* is a private RSA key.
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hashAlgo : hash object
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The hash function to use. This can be a module under `Crypto.Hash`
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or an existing hash object created from any of such modules. If not specified,
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`Crypto.Hash.SHA` (that is, SHA-1) is used.
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mgfunc : callable
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A mask generation function that accepts two parameters: a string to
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use as seed, and the lenth of the mask to generate, in bytes.
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If not specified, the standard MGF1 is used (a safe choice).
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label : string
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A label to apply to this particular encryption. If not specified,
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an empty string is used. Specifying a label does not improve
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security.
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:attention: Modify the mask generation function only if you know what you are doing.
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Sender and receiver must use the same one.
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"""
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return PKCS1OAEP_Cipher(key, hashAlgo, mgfunc, label)
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