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Created by
Delan Azabani
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 | #!/usr/bin/env python3
import sys
from functools import reduce, partial
# DES functions deal with key blocks and data blocks
def encrypt(input, key):
return cipher(input, key, range(1, 17))
def decrypt(input, key):
return cipher(input, key, reversed(range(1, 17)))
def cipher(input, key, round_list):
L, R = split(64, permute(64, input, IP))
for subkey in map(partial(schedule, key), round_list):
L, R = R, L ^ feistel(R, subkey)
return permute(64, glue([R, L], 32), FP)
def schedule(key, round):
CD = split(56, permute(64, key, PC1))
CD = map(partial(rotate, 28, offset=sum(SHIFT[:round])), CD)
return permute(56, glue(CD, 28), PC2)
def feistel(right, subkey):
helper = partial(carve, 48, subkey ^ permute(32, right, E))
sextets = [helper(i + 1, i + 6) for i in range(0, 48, 6)]
nibbles = [substitute(*pair) for pair in enumerate(sextets)]
return permute(32, glue(nibbles, 4), P)
def substitute(index, sextet):
row = glue([head(6, sextet, 1), tail(6, sextet, 1)])
return S[index][row][carve(6, sextet, 2, 5)]
# key derivation function (octet precision, big endian, PKCS #5)
def derive_key(file):
# this function is far from ideal!
return int.from_bytes(pkcs5_pad(file.read(8)), 'big')
# block cipher functions (ECB)
def ecb_encrypt(input_file, output_file, key):
for block in plaintext_blocks(input_file):
block = encrypt(block, key)
ciphertext_write(output_file, block)
def ecb_decrypt(input_file, output_file, key):
for block, finished in ciphertext_blocks(input_file):
block = decrypt(block, key)
plaintext_write(output_file, block, finished)
# file I/O functions (octet precision, big endian, PKCS #5)
def plaintext_blocks(file):
while True:
input = file.read(8)
if len(input) == 0: break
else: yield int.from_bytes(pkcs5_pad(input), 'big')
def ciphertext_blocks(file):
finished, current, next = False, None, None
while not finished:
if current is not None:
block = int.from_bytes(current, 'big')
if len(next) < 8: finished = True
yield (block, finished)
current, next = next, file.read(8)
def plaintext_write(file, block, finished):
sequence = block.to_bytes(8, 'big')
if finished: sequence = pkcs5_unpad(sequence)
file.write(sequence)
def ciphertext_write(file, block):
file.write(block.to_bytes(8, 'big'))
# these padding functions (PKCS #5) deal with octets
def pkcs5_pad(input):
return input + bytes([8 - len(input)] * (8 - len(input)))
def pkcs5_unpad(input):
return input[:(8 - input[-1])]
# bitwise functions (MSB is #1)
def carve(width, input, from_index, to_index):
mask = (1 << 1 + to_index - from_index) - 1
return mask & input >> width - to_index
def until(width, input, index):
return carve(width, input, 1, index)
def after(width, input, index):
return carve(width, input, 1 + index, width)
def head(width, input, count):
return until(width, input, count)
def tail(width, input, count):
return after(width, input, width - count)
def upper(width, input):
return head(width, input, width // 2)
def lower(width, input):
return tail(width, input, width // 2)
def split(width, input):
return pam(laitrap([upper, lower], width), input)
def glue(bits, width=1):
return reduce(lambda value, bit: value << width | bit, bits)
def rotate(width, input, offset):
left = after(width, input, offset) << offset
return (tail(width + offset, left, width) |
until(width, input, offset))
def permute(width, input, table):
return glue([1 & input >> width - offset for offset in table])
# functional programming
def pam(functions, *args, **kwargs):
"""Apply functions to one list of arguments."""
return map(lambda f: f(*args, **kwargs), functions)
def laitrap(functions, *args, **kwargs):
"""Partially apply functions to one list of arguments."""
return map(lambda f: partial(f, *args, **kwargs), functions)
# constants for DES from FIPS 46-3
IP = [
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
]
FP = [
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
]
E = [
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
]
S = [
[[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]]
]
P = [
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
]
PC1 = [
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
]
PC2 = [
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
]
SHIFT = [
1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1
]
# the program
def main():
if len(sys.argv) != 3:
die('Usage: des.py encrypt|decrypt <key file>')
key = derive_key(open(sys.argv[2], 'rb'))
actions = { 'encrypt': ecb_encrypt, 'decrypt': ecb_decrypt }
actions[sys.argv[1]](sys.stdin.buffer, sys.stdout.buffer, key)
def die(message, status=1):
print(message, file=sys.stderr)
sys.exit(status)
if __name__ == '__main__':
main()
|
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