Question

Writ a Python Program that illustrate the DES algorithm

1-Not allowed to use any crypto libraries

2- The whole algorithm must be implemented from scratch

2- The code must be properly commented

Please don’t use librae’s or any code on the internet

please do the code for me i have posted this many times

Answer 1

# Hexadecimal to binary conversion
def hexadecimaltobinary(s):
   mp = {'0' : "0000",
       '1' : "0001",
       '2' : "0010",
       '3' : "0011",
       '4' : "0100",
       '5' : "0101",
       '6' : "0110",
       '7' : "0111",
       '8' : "1000",
       '9' : "1001",
       'A' : "1010",
       'B' : "1011",
       'C' : "1100",
       'D' : "1101",
       'E' : "1110",
       'F' : "1111" }
   bin = ""
   for i in range(len(s)):
       bin = bin + mp[s[i]]
   return bin
  
# Binary to hexadecimal conversion
def binarytohexadecimal(s):
   mp = {"0000" : '0',
       "0001" : '1',
       "0010" : '2',
       "0011" : '3',
       "0100" : '4',
       "0101" : '5',
       "0110" : '6',
       "0111" : '7',
       "1000" : '8',
       "1001" : '9',
       "1010" : 'A',
       "1011" : 'B',
       "1100" : 'C',
       "1101" : 'D',
       "1110" : 'E',
       "1111" : 'F' }
   hex = ""
   for i in range(0,len(s),4):
       ch = ""
       ch = ch + s[i]
       ch = ch + s[i + 1]
       ch = ch + s[i + 2]
       ch = ch + s[i + 3]
       hex = hex + mp[ch]
      
   return hex

# Binary to decimal conversion
def bin2dec(binary):
      
   binary1 = binary
   decimal, i, n = 0, 0, 0
   while(binary != 0):
       dec = binary % 10
       decimal = decimal + dec * pow(2, i)
       binary = binary//10
       i += 1
   return decimal

# Decimal to binary conversion
def dec2bin(num):
   res = bin(num).replace("0b", "")
   if(len(res)%4 != 0):
       div = len(res) / 4
       div = int(div)
       counter =(4 * (div + 1)) - len(res)
       for i in range(0, counter):
           res = '0' + res
   return res

# Permute function to rearrange the bits
def permute(k, arr, n):
   permutation = ""
   for i in range(0, n):
       permutation = permutation + k[arr[i] - 1]
   return permutation

# shifting the bits towards left by nth shifts
def shift_left(k, nth_shifts):
   s = ""
   for i in range(nth_shifts):
       for j in range(1,len(k)):
           s = s + k[j]
       s = s + k[0]
       k = s
       s = ""
   return k  

# calculating xow of two strings of binary number a and b
def xor(a, b):
   ans = ""
   for i in range(len(a)):
       if a[i] == b[i]:
           ans = ans + "0"
       else:
           ans = ans + "1"
   return ans

# Table of Position of 64 bits at initail level: Initial Permutation Table
initial_perm = [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]

# Expansion D-box Table
exp_d = [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 ]

# Straight Permutaion Table
per = [ 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 ]

# S-box Table
sbox = [[[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] ] ]
  
# Final Permutaion Table
final_perm = [ 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 ]

def encrypt(pt, rkb, rk):
   pt = hexadecimaltobinary(pt)
  
   # Initial Permutation
   pt = permute(pt, initial_perm, 64)
   print("After inital permutation", binarytohexadecimal(pt))
  
   # Splitting
   left = pt[0:32]
   right = pt[32:64]
   for i in range(0, 16):
       # Expansion D-box: Expanding the 32 bits data into 48 bits
       right_expanded = permute(right, exp_d, 48)
      
       # XOR RoundKey[i] and right_expanded
       xor_x = xor(right_expanded, rkb[i])

       # S-boxex: substituting the value from s-box table by calculating row and column
       sbox_str = ""
       for j in range(0, 8):
           row = bin2dec(int(xor_x[j * 6] + xor_x[j * 6 + 5]))
           col = bin2dec(int(xor_x[j * 6 + 1] + xor_x[j * 6 + 2] + xor_x[j * 6 + 3] + xor_x[j * 6 + 4]))
           val = sbox[j][row][col]
           sbox_str = sbox_str + dec2bin(val)
          
       # Straight D-box: After substituting rearranging the bits
       sbox_str = permute(sbox_str, per, 32)
      
       # XOR left and sbox_str
       result = xor(left, sbox_str)
       left = result
      
       # Swapper
       if(i != 15):
           left, right = right, left
       print("Round ", i + 1, " ", binarytohexadecimal(left), " ", binarytohexadecimal(right), " ", rk[i])
  
   # Combination
   combine = left + right
  
   # Final permutaion: final rearranging of bits to get cipher text
   cipher_text = permute(combine, final_perm, 64)
   return cipher_text

pt = "123456ABCD132536"
key = "AABB09182736CCDD"

# Key generation
# --hex to binary
key = hexadecimaltobinary(key)

# --parity bit drop table
keyp = [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 ]

# getting 56 bit key from 64 bit using the parity bits
key = permute(key, keyp, 56)

# Number of bit shifts
shift_table = [1, 1, 2, 2,
               2, 2, 2, 2,
               1, 2, 2, 2,
               2, 2, 2, 1 ]

# Key- Compression Table : Compression of key from 56 bits to 48 bits
key_comp = [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 ]

# Splitting
left = key[0:28] # rkb for RoundKeys in binary
right = key[28:56] # rk for RoundKeys in hexadecimal

rkb = []
rk = []
for i in range(0, 16):
   # Shifting the bits by nth shifts by checking from shift table
   left = shift_left(left, shift_table[i])
   right = shift_left(right, shift_table[i])
  
   # Combination of left and right string
   combine_str = left + right
  
   # Compression of key from 56 to 48 bits
   round_key = permute(combine_str, key_comp, 48)

   rkb.append(round_key)
   rk.append(binarytohexadecimal(round_key))

print("Encryption")
cipher_text = binarytohexadecimal

(encrypt(pt, rkb, rk))
print("Cipher Text : ",cipher_text)

print("Decryption")
rkb_rev = rkb[::-1]
rk_rev = rk[::-1]
text = binarytohexadecimal(encrypt(cipher_text, rkb_rev, rk_rev))
print("Plain Text : ",text)