#############################################################################
# 				Documentation				    #
#############################################################################

# Author:   Todd Whiteman
# Date:     12th September, 2005
# Verion:   1.2
# Homepage: http://twhiteman.netfirms.com/des.html
#
# This algorithm is a pure python implementation of the DES algorithm.
# It is in 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.
# Thanks to Mario Wolff for pointing out and debugging some triple des CBC errors.
#
"""A pure python implementation of the DES and TRIPLE DES encryption algorithms

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

key  -> String 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 argument, must be supplied if using CBC mode. Must be 8 bytes


Example:
from pyDes import *

data = "Please encrypt my string"
k = des("DESCRYPT", " ", CBC, "\0\0\0\0\0\0\0\0")
d = k.encrypt(data)
print "Encypted string: " + d
print "Decypted string: " + k.decrypt(d)

See the module source (pyDes.py) for more examples of use.
You can slo 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.

"""


# Modes of crypting / cyphering
ECB =	0
CBC =	1


#############################################################################
# 				    DES					    #
#############################################################################
class des:
	"""DES encryption/decrytpion class

	Supports ECB (Electronic Code Book) and CBC (Cypher Block Chaining) modes.

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

	key  -> The encryption key string, must be exactly 8 bytes
	mode -> Optional argument for encryption type, can be either pyDes.ECB
		(Electronic Code Book), pyDes.CBC (Cypher Block Chaining)
	IV   -> Optional string argument, must be supplied if using CBC mode.
		Must be 8 bytes in length.
	"""


	# Permutation and translation tables for DES
	__pc1 = [56, 48, 40, 32, 24, 16,  8,
		  0, 57, 49, 41, 33, 25, 17,
		  9,  1, 58, 50, 42, 34, 26,
		 18, 10,  2, 59, 51, 43, 35,
		 62, 54, 46, 38, 30, 22, 14,
		  6, 61, 53, 45, 37, 29, 21,
		 13,  5, 60, 52, 44, 36, 28,
		 20, 12,  4, 27, 19, 11,  3
	]

	# number left rotations of pc1
	__left_rotations = [
		1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1
	]

	# permuted choice key (table 2)
	__pc2 = [
		13, 16, 10, 23,  0,  4,
		 2, 27, 14,  5, 20,  9,
		22, 18, 11,  3, 25,  7,
		15,  6, 26, 19, 12,  1,
		40, 51, 30, 36, 46, 54,
		29, 39, 50, 44, 32, 47,
		43, 48, 38, 55, 33, 52,
		45, 41, 49, 35, 28, 31
	]

	# initial permutation IP
	__ip = [57, 49, 41, 33, 25, 17, 9,  1,
		59, 51, 43, 35, 27, 19, 11, 3,
		61, 53, 45, 37, 29, 21, 13, 5,
		63, 55, 47, 39, 31, 23, 15, 7,
		56, 48, 40, 32, 24, 16, 8,  0,
		58, 50, 42, 34, 26, 18, 10, 2,
		60, 52, 44, 36, 28, 20, 12, 4,
		62, 54, 46, 38, 30, 22, 14, 6
	]

	# Expansion table for turning 32 bit blocks into 48 bits
	__expansion_table = [
		31,  0,  1,  2,  3,  4,
		 3,  4,  5,  6,  7,  8,
		 7,  8,  9, 10, 11, 12,
		11, 12, 13, 14, 15, 16,
		15, 16, 17, 18, 19, 20,
		19, 20, 21, 22, 23, 24,
		23, 24, 25, 26, 27, 28,
		27, 28, 29, 30, 31,  0
	]

	# The (in)famous S-boxes
	__sbox = [
		# S1
		[14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7,
		 0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8,
		 4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0,
		 15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13],

		# S2
		[15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10,
		 3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5,
		 0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15,
		 13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9],

		# S3
		[10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8,
		 13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1,
		 13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7,
		 1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12],

		# S4
		[7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15,
		 13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9,
		 10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4,
		 3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14],

		# S5
		[2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9,
		 14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6,
		 4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14,
		 11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3],

		# S6
		[12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11,
		 10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8,
		 9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6,
		 4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13],

		# S7
		[4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1,
		 13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6,
		 1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2,
		 6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12],

		# S8
		[13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7,
		 1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2,
		 7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8,
		 2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11],
	]


	# 32-bit permutation function P used on the output of the S-boxes
	__p = [
		15, 6, 19, 20, 28, 11,
		27, 16, 0, 14, 22, 25,
		4, 17, 30, 9, 1, 7,
		23,13, 31, 26, 2, 8,
		18, 12, 29, 5, 21, 10,
		3, 24
	]

	# final permutation IP^-1
	__fp = [
		39,  7, 47, 15, 55, 23, 63, 31,
		38,  6, 46, 14, 54, 22, 62, 30,
		37,  5, 45, 13, 53, 21, 61, 29,
		36,  4, 44, 12, 52, 20, 60, 28,
		35,  3, 43, 11, 51, 19, 59, 27,
		34,  2, 42, 10, 50, 18, 58, 26,
		33,  1, 41,  9, 49, 17, 57, 25,
		32,  0, 40,  8, 48, 16, 56, 24
	]

	# Type of crypting being done
	ENCRYPT =	0x00
	DECRYPT =	0x01

	# Initialisation
	def __init__(self, key, mode=ECB, IV=None):
		if len(key) != 8:
			raise ValueError("Invalid DES key size. Key must be exactly 8 bytes long.")
		self.block_size = 8
		self.key_size = 8
		self.__padding = ''

		# Set the passed in variables
		self.setMode(mode)
		if IV:
			self.setIV(IV)

		self.L = []
		self.R = []
		self.Kn = [ [0] * 48 ] * 16	# 16 48-bit keys (K1 - K16)
		self.final = []

		self.setKey(key)


	def getKey(self):
		"""getKey() -> string"""
		return self.__key

	def setKey(self, key):
		"""Will set the crypting key for this object. Must be 8 bytes."""
		self.__key = key
		self.__create_sub_keys()

	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 getIV(self):
		"""getIV() -> string"""
		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")
		self.__iv = IV

	def getPadding(self):
		"""getPadding() -> string of length 1. Padding character."""
		return self.__padding

	def __String_to_BitList(self, data):
		"""Turn the string data, into a list of bits (1, 0)'s"""
		l = len(data) * 8
		result = [0] * l
		pos = 0
		for c in data:
			i = 7
			ch = ord(c)
			while i >= 0:
				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 += chr(c)
				c = 0
			pos += 1

		return result

	def __permutate(self, table, block):
		"""Permutate this block with the specified table"""
		return 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 = 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 = 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 = 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 = 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)

		# Remove the padding from the last block
		if crypt_type == des.DECRYPT and self.getPadding():
			#print "Removing decrypt pad"
			s = result[-1]
			while s[-1] == self.getPadding():
				s = s[:-1]
			result[-1] = s

		# Return the full crypted string
		return ''.join(result)

	def encrypt(self, data, pad=''):
		"""encrypt(data, [pad]) -> string

		data : String to be encrypted
		pad  : Optional argument for encryption padding. Must only be one byte

		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, the
		data will then be padded to a multiple of 8 bytes with this
		pad character.
		"""
		self.__padding = pad
		return self.crypt(data, des.ENCRYPT)

	def decrypt(self, data, pad=''):
		"""decrypt(data, [pad]) -> string

		data : String to be encrypted
		pad  : Optional argument for decryption padding. Must only be one byte

		The data must be a multiple of 8 bytes and will be decrypted
		with the already specified key. If the optional padding character
		is supplied, then the un-encypted data will have the padding characters
		removed from the end of the string. This pad removal only occurs on the
		last 8 bytes of the data (last data block).
		"""
		self.__padding = pad
		return self.crypt(data, des.DECRYPT)