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Dreace/des.py

Created Jul 7, 2020
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使用 Python 实现 DES 算法
from itertools import chain
from typing import List, Tuple
from .tables import *
class DES:
def __init__(self, key: [str, bytes]):
if isinstance(key, str):
key = key.encode()
if len(key) > 8:
key = key[8:]
elif len(key) < 8:
key += b"".join(b"\x00" for _ in range(8 - len(key)))
key_bit_list = self._bytes_to_bit_list(key)
left_half_key_block = self._transform(key_bit_list, pc1_left_table)
right_half_key_block = self._transform(key_bit_list, pc1_right_table)
sub_key_list = []
for round_index in range(16):
left_half_key_block = self._circle_left_shift(left_half_key_block, key_left_shift_bits[round_index])
right_half_key_block = self._circle_left_shift(right_half_key_block, key_left_shift_bits[round_index])
sub_key_list.append(self._transform(left_half_key_block + right_half_key_block, pc2_table))
self._sub_key_list = sub_key_list
def encrypt(self, plain_text: [str, bytes]):
if isinstance(plain_text, str):
plain_text = plain_text.encode()
plain_text_len = len(plain_text)
if plain_text_len % 8:
plain_text += b"".join(b"\x00" for _ in range(8 - plain_text_len % 8))
encrypted_blocks = []
for block in map(lambda s: plain_text[s:s + 8], range(0, plain_text_len, 8)):
encrypted_blocks.append(self._encrypt_block(self._bytes_to_bit_list(block)))
encrypted_bit_list = list(chain(*encrypted_blocks))
return self._bit_list_to_bytes(encrypted_bit_list)
def decrypt(self, cipher_text: bytes) -> str:
self._sub_key_list.reverse()
plain_text = self.encrypt(cipher_text)
self._sub_key_list.reverse()
return plain_text.decode().rstrip('\0')
def _encrypt_block(self, plain_block: List[int]) -> List[int]:
plain_block = self._transform(plain_block, ip_table)
left_half_block = plain_block[:32]
right_half_block = plain_block[32:]
for round_index in range(16):
left_half_block, right_half_block = right_half_block, \
self._bit_list_xor(
left_half_block,
self._transform(
self._s_box_transform(
self._bit_list_xor(
self._transform(right_half_block,
extend_table),
self._sub_key_list[round_index]
)
), p_table
)
)
return self._transform(right_half_block + left_half_block, fp_table)
@staticmethod
def _transform(raw_list: list, transform_table: List[int]) -> list:
return list(map(lambda index: raw_list[index], transform_table))
@staticmethod
def _bytes_to_bit_list(input_bytes: bytes) -> List[int]:
bit_list = [0] * 8 * len(input_bytes)
index = 0
for char_ascii in input_bytes:
loc = 7
while loc >= 0:
bit_list[index] = 0 if char_ascii & (1 << loc) == 0 else 1
loc -= 1
index += 1
return bit_list
@staticmethod
def _bit_list_to_bytes(bit_list: List[int]) -> bytes:
char_ascii = 0
byte_list = []
for index, bit in enumerate(bit_list):
char_ascii += bit << (7 - index % 8)
if index % 8 == 7:
byte_list.append(char_ascii)
char_ascii = 0
return bytes(byte_list)
@staticmethod
def _circle_left_shift(input_list: list, bits: int) -> list:
return input_list[bits:] + input_list[:bits]
@staticmethod
def _bit_list_xor(left: list, right: list) -> List[str]:
return list(map(lambda x, y: x ^ y, left, right))
@staticmethod
def _s_box_transform(input_list: list) -> list:
transformed = [0 for _ in range(32)]
transformed_index = 0
r = 0
while r < 48:
m = (input_list[r] << 1) + input_list[r + 5]
n = (input_list[r + 1] << 3) + (input_list[r + 2] << 2) + (input_list[r + 3] << 1) + (input_list[r + 4])
s_value = s_box_tables[r // 6][(m << 4) + n]
transformed[transformed_index] = (s_value & 8) >> 3
transformed[transformed_index + 1] = (s_value & 4) >> 2
transformed[transformed_index + 2] = (s_value & 2) >> 1
transformed[transformed_index + 3] = s_value & 1
r += 6
transformed_index += 4
return transformed
ip_table = [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]
fp_table = [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]
extend_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]
pc1_left_table = [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]
pc1_right_table = [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]
pc2_table = [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]
key_left_shift_bits = [1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1]
p_table = [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]
s_box_tables = [[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]]
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