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############################################################################# # Documentation # ############################################################################# # Author: Todd Whiteman # Date: 16th March, 2009 # Verion: 2.0.0 # License: Public Domain - free to do as you wish # Homepage: http://twhiteman.netfirms.com/des.html # # This is a pure python implementation of the DES encryption algorithm. # It's pure python to avoid portability issues, since most DES # implementations are programmed in C (for performance reasons). # # Triple DES class is also implemented, utilising the DES base. Triple DES # is either DES-EDE3 with a 24 byte key, or DES-EDE2 with a 16 byte key. # # See the README.txt that should come with this python module for the # implementation methods used. # # Thanks to: # * David Broadwell for ideas, comments and suggestions. # * Mario Wolff for pointing out and debugging some triple des CBC errors. # * Santiago Palladino for providing the PKCS5 padding technique. # * Shaya for correcting the PAD_PKCS5 triple des CBC errors. # """A pure python implementation of the DES and TRIPLE DES encryption algorithms. Class initialization -------------------- pyDes.des(key, [mode], [IV], [pad], [padmode]) pyDes.triple_des(key, [mode], [IV], [pad], [padmode]) key -> Bytes containing the encryption key. 8 bytes for DES, 16 or 24 bytes for Triple DES mode -> Optional argument for encryption type, can be either pyDes.ECB (Electronic Code Book) or pyDes.CBC (Cypher Block Chaining) IV -> Optional Initial Value bytes, must be supplied if using CBC mode. Length must be 8 bytes. pad -> Optional argument, set the pad character (PAD_NORMAL) to use during all encrypt/decrpt operations done with this instance. padmode -> Optional argument, set the padding mode (PAD_NORMAL or PAD_PKCS5) to use during all encrypt/decrpt operations done with this instance. I recommend to use PAD_PKCS5 padding, as then you never need to worry about any padding issues, as the padding can be removed unambiguously upon decrypting data that was encrypted using PAD_PKCS5 padmode. Common methods -------------- encrypt(data, [pad], [padmode]) decrypt(data, [pad], [padmode]) data -> Bytes to be encrypted/decrypted pad -> Optional argument. Only when using padmode of PAD_NORMAL. For encryption, adds this characters to the end of the data block when data is not a multiple of 8 bytes. For decryption, will remove the trailing characters that match this pad character from the last 8 bytes of the unencrypted data block. padmode -> Optional argument, set the padding mode, must be one of PAD_NORMAL or PAD_PKCS5). Defaults to PAD_NORMAL. Example ------- from pyDes import * data = "Please encrypt my data" k = des("DESCRYPT", CBC, "\0\0\0\0\0\0\0\0", pad=None, padmode=PAD_PKCS5) # For Python3, you'll need to use bytes, i.e.: # data = b"Please encrypt my data" # k = des(b"DESCRYPT", CBC, b"\0\0\0\0\0\0\0\0", pad=None, padmode=PAD_PKCS5) d = k.encrypt(data) print "Encrypted: %r" % d print "Decrypted: %r" % k.decrypt(d) assert k.decrypt(d, padmode=PAD_PKCS5) == data See the module source (pyDes.py) for more examples of use. You can also run the pyDes.py file without and arguments to see a simple test. Note: This code was not written for high-end systems needing a fast implementation, but rather a handy portable solution with small usage. """ import sys # _pythonMajorVersion is used to handle Python2 and Python3 differences. _pythonMajorVersion = sys.version_info[0] # Modes of crypting / cyphering ECB = 0 CBC = 1 # Modes of padding PAD_NORMAL = 1 PAD_PKCS5 = 2 # PAD_PKCS5: is a method that will unambiguously remove all padding # characters after decryption, when originally encrypted with # this padding mode. # For a good description of the PKCS5 padding technique, see: # http://www.faqs.org/rfcs/rfc1423.html # The base class shared by des and triple des. class _baseDes(object): def __init__(self, mode=ECB, IV=None, pad=None, padmode=PAD_NORMAL): if IV: IV = self._guardAgainstUnicode(IV) if pad: pad = self._guardAgainstUnicode(pad) self.block_size = 8 # Sanity checking of arguments. if pad and padmode == PAD_PKCS5: raise ValueError("Cannot use a pad character with PAD_PKCS5") if IV and len(IV) != self.block_size: raise ValueError("Invalid Initial Value (IV), must be a multiple of " + str(self.block_size) + " bytes") # Set the passed in variables self._mode = mode self._iv = IV self._padding = pad self._padmode = padmode def getKey(self): """getKey() -> bytes""" return self.__key def setKey(self, key): """Will set the crypting key for this object.""" key = self._guardAgainstUnicode(key) self.__key = key def getMode(self): """getMode() -> pyDes.ECB or pyDes.CBC""" return self._mode def setMode(self, mode): """Sets the type of crypting mode, pyDes.ECB or pyDes.CBC""" self._mode = mode def getPadding(self): """getPadding() -> bytes of length 1. Padding character.""" return self._padding def setPadding(self, pad): """setPadding() -> bytes of length 1. Padding character.""" if pad is not None: pad = self._guardAgainstUnicode(pad) self._padding = pad def getPadMode(self): """getPadMode() -> pyDes.PAD_NORMAL or pyDes.PAD_PKCS5""" return self._padmode def setPadMode(self, mode): """Sets the type of padding mode, pyDes.PAD_NORMAL or pyDes.PAD_PKCS5""" self._padmode = mode def getIV(self): """getIV() -> bytes""" return self._iv def setIV(self, IV): """Will set the Initial Value, used in conjunction with CBC mode""" if not IV or len(IV) != self.block_size: raise ValueError("Invalid Initial Value (IV), must be a multiple of " + str(self.block_size) + " bytes") IV = self._guardAgainstUnicode(IV) self._iv = IV def _padData(self, data, pad, padmode): # Pad data depending on the mode if padmode is None: # Get the default padding mode. padmode = self.getPadMode() if pad and padmode == PAD_PKCS5: raise ValueError("Cannot use a pad character with PAD_PKCS5") if padmode == PAD_NORMAL: if len(data) % self.block_size == 0: # No padding required. return data if not pad: # Get the default padding. pad = self.getPadding() if not pad: raise ValueError("Data must be a multiple of " + str(self.block_size) + " bytes in length. Use padmode=PAD_PKCS5 or set the pad character.") data += (self.block_size - (len(data) % self.block_size)) * pad elif padmode == PAD_PKCS5: pad_len = 8 - (len(data) % self.block_size) if _pythonMajorVersion < 3: data += pad_len * chr(pad_len) else: data += bytes([pad_len] * pad_len) return data def _unpadData(self, data, pad, padmode): # Unpad data depending on the mode. if not data: return data if pad and padmode == PAD_PKCS5: raise ValueError("Cannot use a pad character with PAD_PKCS5") if padmode is None: # Get the default padding mode. padmode = self.getPadMode() if padmode == PAD_NORMAL: if not pad: # Get the default padding. pad = self.getPadding() if pad: data = data[:-self.block_size] + \ data[-self.block_size:].rstrip(pad) elif padmode == PAD_PKCS5: if _pythonMajorVersion < 3: pad_len = ord(data[-1]) else: pad_len = data[-1] data = data[:-pad_len] return data def _guardAgainstUnicode(self, data): # Only accept byte strings or ascii unicode values, otherwise # there is no way to correctly decode the data into bytes. if _pythonMajorVersion < 3: if isinstance(data, unicode): raise ValueError("pyDes can only work with bytes, not Unicode strings.") else: if isinstance(data, str): # Only accept ascii unicode values. try: return data.encode('ascii') except UnicodeEncodeError: pass raise ValueError("pyDes can only work with encoded strings, not Uni