pydes.py

A pure python module which implements the DES and Triple-DES encryption algorithms. Triple DES is ei

				if ch & (1 << i) != 0:
					result[pos] = 1
				else:
					result[pos] = 0
				pos += 1
				i -= 1

		return result

	def __BitList_to_String(self, data):
		"""Turn the list of bits -> data, into a string"""
		result = []
		pos = 0
		c = 0
		while pos < len(data):
			c += data[pos] << (7 - (pos % 8))
			if (pos % 8) == 7:
				result.append(c)
				c = 0
			pos += 1

		if _pythonMajorVersion < 3:
			return ''.join([ chr(c) for c in result ])
		else:
			return bytes(result)

	def __permutate(self, table, block):
		"""Permutate this block with the specified table"""
		return list(map(lambda x: block[x], table))
	
	# Transform the secret key, so that it is ready for data processing
	# Create the 16 subkeys, K[1] - K[16]
	def __create_sub_keys(self):
		"""Create the 16 subkeys K[1] to K[16] from the given key"""
		key = self.__permutate(des.__pc1, self.__String_to_BitList(self.getKey()))
		i = 0
		# Split into Left and Right sections
		self.L = key[:28]
		self.R = key[28:]
		while i < 16:
			j = 0
			# Perform circular left shifts
			while j < des.__left_rotations[i]:
				self.L.append(self.L[0])
				del self.L[0]

				self.R.append(self.R[0])
				del self.R[0]

				j += 1

			# Create one of the 16 subkeys through pc2 permutation
			self.Kn[i] = self.__permutate(des.__pc2, self.L + self.R)

			i += 1

	# Main part of the encryption algorithm, the number cruncher :)
	def __des_crypt(self, block, crypt_type):
		"""Crypt the block of data through DES bit-manipulation"""
		block = self.__permutate(des.__ip, block)
		self.L = block[:32]
		self.R = block[32:]

		# Encryption starts from Kn[1] through to Kn[16]
		if crypt_type == des.ENCRYPT:
			iteration = 0
			iteration_adjustment = 1
		# Decryption starts from Kn[16] down to Kn[1]
		else:
			iteration = 15
			iteration_adjustment = -1

		i = 0
		while i < 16:
			# Make a copy of R[i-1], this will later become L[i]
			tempR = self.R[:]

			# Permutate R[i - 1] to start creating R[i]
			self.R = self.__permutate(des.__expansion_table, self.R)

			# Exclusive or R[i - 1] with K[i], create B[1] to B[8] whilst here
			self.R = list(map(lambda x, y: x ^ y, self.R, self.Kn[iteration]))
			B = [self.R[:6], self.R[6:12], self.R[12:18], self.R[18:24], self.R[24:30], self.R[30:36], self.R[36:42], self.R[42:]]
			# Optimization: Replaced below commented code with above
			#j = 0
			#B = []
			#while j < len(self.R):
			#	self.R[j] = self.R[j] ^ self.Kn[iteration][j]
			#	j += 1
			#	if j % 6 == 0:
			#		B.append(self.R[j-6:j])

			# Permutate B[1] to B[8] using the S-Boxes
			j = 0
			Bn = [0] * 32
			pos = 0
			while j < 8:
				# Work out the offsets
				m = (B[j][0] << 1) + B[j][5]
				n = (B[j][1] << 3) + (B[j][2] << 2) + (B[j][3] << 1) + B[j][4]

				# Find the permutation value
				v = des.__sbox[j][(m << 4) + n]

				# Turn value into bits, add it to result: Bn
				Bn[pos] = (v & 8) >> 3
				Bn[pos + 1] = (v & 4) >> 2
				Bn[pos + 2] = (v & 2) >> 1
				Bn[pos + 3] = v & 1

				pos += 4
				j += 1

			# Permutate the concatination of B[1] to B[8] (Bn)
			self.R = self.__permutate(des.__p, Bn)

			# Xor with L[i - 1]
			self.R = list(map(lambda x, y: x ^ y, self.R, self.L))
			# Optimization: This now replaces the below commented code
			#j = 0
			#while j < len(self.R):
			#	self.R[j] = self.R[j] ^ self.L[j]
			#	j += 1

			# L[i] becomes R[i - 1]
			self.L = tempR

			i += 1
			iteration += iteration_adjustment
		
		# Final permutation of R[16]L[16]
		self.final = self.__permutate(des.__fp, self.R + self.L)
		return self.final


	# Data to be encrypted/decrypted
	def crypt(self, data, crypt_type):
		"""Crypt the data in blocks, running it through des_crypt()"""

		# Error check the data
		if not data:
			return ''
		if len(data) % self.block_size != 0:
			if crypt_type == des.DECRYPT: # Decryption must work on 8 byte blocks
				raise ValueError("Invalid data length, data must be a multiple of " + str(self.block_size) + " bytes\n.")
			if not self.getPadding():
				raise ValueError("Invalid data length, data must be a multiple of " + str(self.block_size) + " bytes\n. Try setting the optional padding character")
			else:
				data += (self.block_size - (len(data) % self.block_size)) * self.getPadding()
			# print "Len of data: %f" % (len(data) / self.block_size)

		if self.getMode() == CBC:
			if self.getIV():
				iv = self.__String_to_BitList(self.getIV())
			else:
				raise ValueError("For CBC mode, you must supply the Initial Value (IV) for ciphering")

		# Split the data into blocks, crypting each one seperately
		i = 0
		dict = {}
		result = []
		#cached = 0
		#lines = 0
		while i < len(data):
			# Test code for caching encryption results
			#lines += 1
			#if dict.has_key(data[i:i+8]):
				#print "Cached result for: %s" % data[i:i+8]
			#	cached += 1
			#	result.append(dict[data[i:i+8]])
			#	i += 8
			#	continue
				
			block = self.__String_to_BitList(data[i:i+8])

			# Xor with IV if using CBC mode
			if self.getMode() == CBC:
				if crypt_type == des.ENCRYPT:
					block = list(map(lambda x, y: x ^ y, block, iv))
					#j = 0
					#while j < len(block):
					#	block[j] = block[j] ^ iv[j]
					#	j += 1

				processed_block = self.__des_crypt(block, crypt_type)

				if crypt_type == des.DECRYPT:
					processed_block = list(map(lambda x, y: x ^ y, processed_block, iv))
					#j = 0
					#while j < len(processed_block):
					#	processed_block[j] = processed_block[j] ^ iv[j]
					#	j += 1
					iv = block
				else:
					iv = processed_block
			else:
				processed_block = self.__des_crypt(block, crypt_type)


			# Add the resulting crypted block to our list
			#d = self.__BitList_to_String(processed_block)
			#result.append(d)
			result.append(self.__BitList_to_String(processed_block))
			#dict[data[i:i+8]] = d
			i += 8

		# print "Lines: %d, cached: %d" % (lines, cached)

		# Return the full crypted string
		if _pythonMajorVersion < 3:
			return ''.join(result)
		else:
			return bytes.fromhex('').join(result)

	def encrypt(self, data, pad=None, padmode=None):
		"""encrypt(data, [pad], [padmode]) -> bytes

		data : Bytes to be encrypted
		pad  : Optional argument for encryption padding. Must only be one byte
		padmode : Optional argument for overriding the padding mode.

		The data must be a multiple of 8 bytes and will be encrypted
		with the already specified key. Data does not have to be a
		multiple of 8 bytes if the padding character is supplied, or
		the padmode is set to PAD_PKCS5, as bytes will then added to
		ensure the be padded data is a multiple of 8 bytes.
		"""
		data = self._guardAgainstUnicode(data)
		if pad is not None:
			pad = self._guardAgainstUnicode(pad)
		data = self._padData(data, pad, padmode)
		return self.crypt(data, des.ENCRYPT)

	def decrypt(self, data, pad=None, padmode=None):
		"""decrypt(data, [pad], [padmode]) -> bytes

		data : Bytes to be encrypted
		pad  : Optional argument for decryption padding. Must only be one byte
		padmode : Optional argument for overriding the padding mode.

		The data must be a multiple of 8 bytes and will be decrypted
		with the already specified key. In PAD_NORMAL mode, if the
		optional padding character is supplied, then the un-encrypted
		data will have the padding characters removed from the end of
		the bytes. This pad removal only occurs on the last 8 bytes of
		the data (last data block). In PAD_PKCS5 mode, the special
		padding end markers will be removed from the data after decrypting.
		"""
		data = self._guardAgainstUnicode(data)
		if pad is not None:
			pad = self._guardAgainstUnicode(pad)
		data = self.crypt(data, des.DECRYPT)
		return self._unpadData(data, pad, padmode)



#############################################################################
# 				Triple DES				    #
#############################################################################
class triple_des(_baseDes):
	"""Triple DES encryption/decrytpion class

	This algorithm uses the DES-EDE3 (when a 24 byte key is supplied) or
	the DES-EDE2 (when a 16 byte key is supplied) encryption methods.
	Supports ECB (Electronic Code Book) and CBC (Cypher Block Chaining) modes.

	pyDes.des(key, [mode], [IV])

	key  -> Bytes containing the encryption key, must be either 16 or
	        24 bytes long
	mode -> Optional argument for encryption type, can be either pyDes.ECB
		(Electronic Code Book), pyDes.CBC (Cypher Block Chaining)
	IV   -> Optional Initial Value bytes, must be supplied if using CBC mode.
		Must be 8 bytes in length.
	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.
	"""
	def __init__(self, key, mode=ECB, IV=None, pad=None, padmode=PAD_NORMAL):
		_baseDes.__init__(self, mode, IV, pad, padmode)
		self.setKey(key)

	def setKey(self, key):
		"""Will set the crypting key for this object. Either 16 or 24 bytes long."""
		self.key_size = 24  # Use DES-EDE3 mode
		if len(key) != self.key_size:
			if len(key) == 16: # Use DES-EDE2 mode
				self.key_size = 16
			else:
				raise ValueError("Invalid triple DES key size. Key must be either 16 or 24 bytes long")
		if self.getMode() == CBC:
			if not self.getIV():
				# Use the first 8 bytes of the key
				self.setIV(key[:self.block_size])
			if len(self.getIV()) != self.block_size:
				raise ValueError("Invalid IV, must be 8 bytes in length")
		self.__key1 = des(key[:8], self._mode, self._iv,
				  self._padding, self._padmode)
		self.__key2 = des(key[8:16], self._mode, self._iv,
				  self._padding, self._padmode)
		if self.key_size == 16:
			self.__key3 = self.__key1
		else:
			self.__key3 = des(key[16:], self._mode, self._iv,
					  self._padding, self._padmode)
		_baseDes.setKey(self, key)

	# Override setter methods to work on all 3 keys.

	def setMode(self, mode):
		"""Sets the type of crypting mode, pyDes.ECB or pyDes.CBC"""
		_baseDes.setMode(self, mode)
		for key in (self.__key1, self.__key2, self.__key3):
			key.setMode(mode)

	def setPadding(self, pad):
		"""setPadding() -> bytes of length 1. Padding character."""
		_baseDes.setPadding(self, pad)
		for key in (self.__key1, self.__key2, self.__key3):
			key.setPadding(pad)

	def setPadMode(self, mode):
		"""Sets the type of padding mode, pyDes.PAD_NORMAL or pyDes.PAD_PKCS5"""
		_baseDes.setPadMode(self, mode)
		for key in (self.__key1, self.__key2, self.__key3):
			key.setPadMode(mode)

	def setIV(self, IV):
		"""Will set the Initial Value, used in conjunction with CBC mode"""
		_baseDes.setIV(self, IV)
		for key in (self.__key1, self.__key2, self.__key3):
			key.setIV(IV)

	def encrypt(self, data, pad=None, padmode=None):
		"""encrypt(data, [pad], [padmode]) -> bytes

		data : bytes to be encrypted
		pad  : Optional argument for encryption padding. Must only be one byte
		padmode : Optional argument for overriding the padding mode.

		The data must be a multiple of 8 bytes and will be encrypted
		with the already specified key. Data does not have to be a
		multiple of 8 bytes if the padding character is supplied, or
		the padmode is set to PAD_PKCS5, as bytes will then added to
		ensure the be padded data is a multiple of 8 bytes.
		"""
		ENCRYPT = des.ENCRYPT
		DECRYPT = des.DECRYPT
		data = self._guardAgainstUnicode(data)
		if pad is not None:
			pad = self._guardAgainstUnicode(pad)
		# Pad the data accordingly.
		data = self._padData(data, pad, padmode)
		if self.getMode() == CBC:
			self.__key1.setIV(self.getIV())
			self.__key2.setIV(self.getIV())
			self.__key3.setIV(self.getIV())
			i = 0
			result = []
			while i < len(data):
				block = self.__key1.crypt(data[i:i+8], ENCRYPT)
				block = self.__key2.crypt(block, DECRYPT)
				block = self.__key3.crypt(block, ENCRYPT)
				self.__key1.setIV(block)
				self.__key2.setIV(block)
				self.__key3.setIV(block)
				result.append(block)
				i += 8
			if _pythonMajorVersion < 3:
				return ''.join(result)
			else:
				return bytes.fromhex('').join(result)
		else:
			data = self.__key1.crypt(data, ENCRYPT)
			data = self.__key2.crypt(data, DECRYPT)
			return self.__key3.crypt(data, ENCRYPT)

	def decrypt(self, data, pad=None, padmode=None):
		"""decrypt(data, [pad], [padmode]) -> bytes

		data : bytes to be encrypted
		pad  : Optional argument for decryption padding. Must only be one byte
		padmode : Optional argument for overriding the padding mode.

		The data must be a multiple of 8 bytes and will be decrypted
		with the already specified key. In PAD_NORMAL mode, if the
		optional padding character is supplied, then the un-encrypted
		data will have the padding characters removed from the end of
		the bytes. This pad removal only occurs on the last 8 bytes of
		the data (last data block). In PAD_PKCS5 mode, the special
		padding end markers will be removed from the data after
		decrypting, no pad character is required for PAD_PKCS5.
		"""
		ENCRYPT = des.ENCRYPT
		DECRYPT = des.DECRYPT
		data = self._guardAgainstUnicode(data)
		if pad is not None:
			pad = self._guardAgainstUnicode(pad)
		if self.getMode() == CBC:
			self.__key1.setIV(self.getIV())
			self.__key2.setIV(self.getIV())
			self.__key3.setIV(self.getIV())
			i = 0
			result = []
			while i < len(data):
				iv = data[i:i+8]
				block = self.__key3.crypt(iv,    DECRYPT)
				block = self.__key2.crypt(block, ENCRYPT)
				block = self.__key1.crypt(block, DECRYPT)
				self.__key1.setIV(iv)
				self.__key2.setIV(iv)
				self.__key3.setIV(iv)
				result.append(block)
				i += 8
			if _pythonMajorVersion < 3:
				data = ''.join(result)
			else:
				data = bytes.fromhex('').join(result)
		else:
			data = self.__key3.crypt(data, DECRYPT)
			data = self.__key2.crypt(data, ENCRYPT)
			data = self.__key1.crypt(data, DECRYPT)
		return self._unpadData(data, pad, padmode)