DES_Algorithm

ciphers/des_algorithm.py

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+'''It is highly recommended to visit this page before trying to run the code,
+ all the function names then would be self explanatory thereafter
+ https://en.wikipedia.org/wiki/Data_Encryption_Standard .
+ This class provides various functions for the DES algorithm implementation,
+ import this class to use these functions.
+'''
+
+
+class DesAlgo:
+ initial_permutation = [58, 50, 42, 34, 26, 18, 10,
+ 2, 60, 52, 44, 36, 28, 20,
+ 12, 4, 62, 54, 46, 38, 30, 22,
+ 14, 6, 64, 56, 48, 40, 32,
+ 24, 16, 8, 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]
+ inverse_permutaion = [40, 8, 48, 16, 56, 24, 64, 32,
+ 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]
+ exp_table = [32, 1, 2, 3, 4, 5, 4, 5, 6, 7, 8, 9, 8,
+ 9, 10, 11, 12, 13, 12, 13, 14, 15, 16, 17,
+ 16, 17, 18, 19, 20, 21, 20, 21, 22, 23, 24,
+ 25, 24, 25, 26, 27, 28, 29, 28, 29, 30, 31, 32, 1]
+ pc1_table = [57, 49, 41, 33, 25, 17, 9, 1, 58, 50,
+ 42, 34, 26, 18, 10, 2, 59, 51, 43, 35,
+ 27, 19, 11, 3, 60, 52, 44,
+ 36, 63, 55, 47, 39, 31, 23, 15,
+ 7, 62, 54, 46, 38, 30, 22, 14, 6, 61,
+ 53, 45, 37, 29, 21, 13, 5, 28, 20, 12, 4]
+ shifts = [1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1]
+ bit_shuffle = [16, 7, 20, 21, 29, 12, 28, 17, 1, 15, 23, 26, 5, 18,
+ 31, 10, 2, 8, 24, 14, 32, 27, 3, 9, 19, 13, 30, 6,
+ 22, 11, 4, 25]
+ pc2_table = [14, 17, 11, 24, 1, 5, 3, 28, 15, 6, 21, 10,
+ 23, 19, 12, 4, 26, 8, 16, 7, 27, 20, 13,
+ 2, 41, 52, 31, 37, 47, 55, 30, 40, 51, 45,
+ 33, 48, 44, 49, 39, 56, 34, 53, 46, 42, 50, 36, 29, 32]
+ keys = list()
+ shifted_keys = list()
+ s_boxes = [[
+ [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]
+ ],
+ [
+ [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]
+ ],
+ [
+ [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]
+ ],
+ [
+ [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]
+ ],
+ [
+ [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]
+ ],
+ [
+ [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]
+ ],
+ [
+ [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]
+ ],
+ [
+ [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]
+ ]]
+
+ def single_string(self, s: str) -> str:
+ return ''.join(s.split())
+
+ def hex_to_bin(self, n: str) -> str:
+ return bin(int(n, 16))
+
+ def bin_to_hex(self, n: str) -> str:
+ n = self.single_string(n)
+ temp = hex(int(n, 2))[2:]
+ return '0' * (16 - len(temp)) + temp
+
+ # constructs the str by looking up the corresponding table
+ def crank(self, msg, table: list(int)) -> str:
+ msg = self.single_string(msg)
+ s = ''
+ for i in range(len(table)):
+ s += msg[table[i] - 1]
+ return s
+
+ # makes long str presentable
+ def pretty(self, s: str) -> str:
+ s = self.single_string(s)
+ t = ''
+ i = 0
+ if len(s) == 64 or len(s) == 16:
+ i = 4
+ else:
+ i = len(s) // 8
+ for j in range(i, len(s) + 1, i):
+ t += s[j - i:j] + ' '
+ return t
+
+ def initial_permutations(self, msg: str) -> str:
+ return self.crank(self.single_string(msg), self.initial_permutation)
+
+ def inverse_permutation(self, msg: str) -> str:
+ return self.crank(self.single_string(msg), self.inverse_permutaion)
+
+ def expansion(self, msg: str) -> str:
+ return self.crank(self.single_string(msg), self.exp_table)
+
+ def key_to_fifty_six(self, key: str) -> str:
+ key = self.single_string(key)
+ t = ''
+ for i in range(len(key)):
+ if i == 0 or i % 8 != 0:
+ t += key[i]
+ return t
+
+ def pc1(self, key: str) -> str:
+ return self.crank(self.single_string(key), self.pc1_table)
+
+ def shift_left(self, key: str, rnd: int) -> str:
+ key = self.single_string(key)
+ left = key[0:28]
+ right = key[28:]
+ i = self.shifts[rnd - 1]
+ return (left[i:len(left)] + left[0:i]) + (right[i:len(right)] + right[0:i])
+
+ def pc2(self, key):
+ return self.crank(self.single_string(key), self.pc2_table)
+
+ def xor(self, s1: str, s2: str) -> str:
+ s1 = self.single_string(s1)
+ s2 = self.single_string(s2)
+ ans = ''
+ for i in range(len(s1)):
+ ans += str(int(s1[i]) ^ int(s2[i]))
+ return ans
+
+ def s_box(self, msg: str) -> str:
+ msg = self.single_string(msg)
+ ans, n = '', 0
+ for i in range(0, 48, 6):
+ temp = msg[i:i + 6]
+ row = int(temp[0] + temp[5], 2)
+ col = int(temp[1:5], 2)
+ code = bin(self.s_boxes[n][row][col])[2:]
+ ans += '0' * (4 - len(code)) + code
+ n += 1
+ return ans
+
+ def bits_shuffle(self, msg: str) -> str:
+ return self.crank(self.single_string(msg), self.bit_shuffle)
+
+ def generate_keys(self, key: str) -> str:
+ key = self.single_string(key)
+ key = self.pc1(key)
+ print(self.pretty(key))
+ for i in range(16):
+ key = self.shift_left(key, i + 1)
+ self.shifted_keys.append(key)
+ self.keys.append(self.pc2(key))
+
+ def solve(self, msg: str, key: str, rnd: int) -> str:
+ msg = self.single_string(msg)
+ key = self.single_string(key)
+ r_half, l_half = '', ''
+ print("Input message m:")
+ print(self.pretty(msg))
+ print("After applying initial permutation we get:")
+ msg = self.initial_permutations(msg)
+ print(self.pretty(msg))
+ print("After applying message expansion to the right half, we get:")
+ r_half = msg[32:]
+ l_half = msg[0:32]
+ r_half = self.expansion(r_half)
+ print(self.pretty(r_half))
+ print("Given key string is given below:")
+ print(self.pretty(key))
+ print("Now applying PC-1 we get: ")
+ key = self.pc1(key)
+ print(self.pretty(key))
+ print(f"Rotating {self.shifts[rnd]} bit to the left we get:")
+ key = self.shift_left(key, rnd)
+ print(self.pretty(key))
+ print("Applying PC-2 we get:")
+ key = self.pc2(key)
+ print(self.pretty(key))
+ print("Xor-ing with right half:")
+ r_half = self.xor(r_half, key)
+ print(self.pretty(r_half))
+ print("Applying S-box we get:")
+ r_half = self.s_box(r_half)
+ print(self.pretty(r_half))
+ print("Applying bit shuffling we get:")
+ r_half = self.bits_shuffle(r_half)
+ print(self.pretty(r_half))
+ print("Now Xor-ing with left half will give:")
+ r_half = self.xor(r_half, l_half)
+ print(self.pretty(r_half))
+ print("Encrypted message for this rnd is:")
+ print('Binary:\n' + self.pretty(l_half) + self.pretty(r_half))
+ print('Hex:\n' + self.pretty(self.bin_to_hex(msg[32:] + r_half)))
+ return msg[32:] + r_half