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Des.py
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import textwrap
PermutationCombinationA = [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]
PermutationCombinationB = [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]
ExpansionList = [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]
SBoxes =\
[
[
[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]
]
]
PermutationList = [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]
InitialPermutationList = \
['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']
InversePermutationList = \
['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 applyPermutationCombinationA(pc1_table, keys_64bits):
""" This function takes Permutation table and initial key as input and return 56 bits key as output"""
keys_56bits = ""
for index in pc1_table:
keys_56bits += keys_64bits[index-1]
return keys_56bits
def splitInHalf(key):
""" Split the key into two equal half """
half = len(key)
left_keys, right_keys = key[:half],keys[half:]
return left_keys, right_keys
def circularLeftShift(bits, numberofbits):
"""This method will circularly shift the given bit string according to the number of bits"""
shiftedbits = bits[numberofbits:] + bits[:numberofbits]
return shiftedbits
def applyCompression(pc2_table, keys_56bits):
""" This will take Compression table and combined both half as input and return a 48-bits string as output"""
keys_48bits = ""
for index in pc2_table:
keys_48bits += keys_56bits[index-1]
return keys_48bits
def generateKeys(key):
""" Generates multiple keys from the initial 64 bit key"""
round_keys = list()
out = applyPermutationCombinationA(PermutationCombinationA, key)
L0, R0 = splitInHalf(out)
for roundnumber in range(16):
newL = circularLeftShift(L0, Shifts[roundnumber])
newR = circularLeftShift(R0, Shifts[roundnumber])
roundkey = applyCompression(PermutationCombinationB, newL + newR)
round_keys.append(roundkey)
L0 = newL
R0 = newR
return round_keys
def applyExpansion(expansion_table, bits32):
""" This will take expansion table and 32-bit binary string as input and output a 48-bit binary stirng"""
bits48 = ""
for index in expansion_table:
bits48 += bits32[index-1]
return bits48
def XOR(bits1,bits2):
"""perform a XOR operation and return the output"""
xor_result = ""
for index in range(len(bits1)):
if bits1[index] == bits2[index]:
xor_result += '0'
else:
xor_result += '1'
return xor_result
def splitInSixBits(XOR_48bits):
"""split 48 bits into 6 bits each """
list_of_6bits = textwrap.wrap(XOR_48bits, 6)
return list_of_6bits
def getFirstAndLastBit(bits6):
"""Return first and last bit from a binary string"""
twobits = bits6[0] + bits6[-1]
return twobits
def getMiddleFourBits(bits6):
"""Return first and last bit from a binary string"""
fourbits = bits6[1:5]
return fourbits
def binaryToDecimal(binarybits):
""" Convert binary bits to decimal"""
# helps during list access
decimal = int(binarybits, 2)
return decimal
def decimalToBinary(decimal):
""" Convert decimal to binary bits"""
binary4bits = bin(decimal)[2:].zfill(4)
return binary4bits
def sboxLookup(sboxcount, first_last, middle4):
""" take three parameter and access the Sbox accordingly and return the value"""
d_first_last = binaryToDecimal(first_last)
d_middle = binaryToDecimal(middle4)
sbox_value = SBoxes[sboxcount][d_first_last][d_middle]
return decimalToBinary(sbox_value)
def applyPermutation(permutation_table, sbox_32bits):
""" It takes Sboxes output and a permutation table and return 32 bit binary string"""
final_32bits = ""
for index in permutation_table:
final_32bits += sbox_32bits[index-1]
return final_32bits
def fFunction(pre32bits, key48bits):
"""This is main function to perform function F """
result = ""
expanded_left_half = applyExpansion(ExpansionList, pre32bits)
xor_value = XOR(expanded_left_half,key48bits)
bits6list = splitInSixBits(xor_value)
for sboxcount, bits6 in enumerate(bits6list):
first_last = getFirstAndLastBit(bits6)
middle4 = getMiddleFourBits(bits6)
sboxvalue = sboxLookup(sboxcount, first_last, middle4)
result += sboxvalue
final32bits = applyPermutation(PermutationList, result)
return final32bits
def hexTobinary(hexdigits):
""" Converts Hexadecimal digits to Binary"""
binarydigits = ""
for hexdigit in hexdigits:
binarydigits += bin(int(hexdigit,16))[2:].zfill(4)
return binarydigits
def apply_p(table, text):
""" Apply permutation"""
permutated_M = ""
for index in table:
permutated_M += text[int(index)-1]
return permutated_M
def DES_encrypt(message, key):
""" Takes in the message and key. Encrypts the message using the DES algorithm. Returns the encrypted message."""
key_bits = hexTobinary(key)
roundkeys = generateKeys(key_bits)
p_plaintext = apply_p(InitialPermutationList, message)
L, R = splitInHalf(p_plaintext)
for round in range(16):
newR = XOR(L, fFunction(R, roundkeys[round]))
newL = R
R = newR
L = newL
cipher = apply_p(InversePermutationList, R + L)
return cipher
def DES_decrypt(ciphertext, key):
""" Takes in the ciphertext and key. Decrypts the ciphertext using the DES algorithm. Returns the decrypted message."""
key_bits = hexTobinary(key)
roundkeys = generateKeys(key_bits)
p_ciphertext = apply_p(InitialPermutationList, ciphertext)
L, R = spliHalf(p_ciphertext)
for round in range(16):
newR = XOR(L, fFunction(R, roundkeys[15-round]))
newL = R
R = newR
L = newL
message = apply_p(InversePermutationList, R + L)
return message