Python实现DES加密算法

　　这是学校专业课程设计，要求实现112位的密钥长度的DES算法，与原有的DES算法不同的是密钥长度不懂，
　　但是每轮的子密钥长度依然是56（64）位的。由于那阶段事情较多，为了早些完成，就选用的Python编程语言，
　　参考了一个小都开源代码pydes，有兴趣都可以看看。
　　说实话，用Python写代码真是一种享受！尤其是表置换，只需要一句代码即可！
　　下面正文：
要求：对DES密码系统进行改进，延长密钥长度为112比特，取两个各位64比特的密钥K1,K2,在DES的第1到5轮
使用K1密钥产生的子密钥，在第6到11轮使用K2密钥产生的子密钥，在第12到16轮使用K1密钥产生余下的子密钥。
实现112位的DES加密算法，实验关于明文与密钥的雪崩效应。
DES算法流程图

　　
　　一轮DES过程

　　知道DES算法实现方式后就可以写代码了
　　真正用于给别人使用的DES算法需要考虑很多
　　对称加密算法要求被加密数据时分块的，这就需要数据对齐，从而引入了几种大家公认的填充方式
　　还有就是初始向量
　　



  1 #coding=gbk
  2 #Author :  xddy1008@gmail.com
  3
  4
  5
  6 #Type of crypting being done
  7 ENCRYPT =    0x00
  8 DECRYPT =    0x01
  9
10 # Permutation and translation tables for DES
11 # 密钥置换
12 __pc1 = [56, 48, 40, 32, 24, 16,  8,
13         0, 57, 49, 41, 33, 25, 17,
14         9,  1, 58, 50, 42, 34, 26,
15         18, 10,  2, 59, 51, 43, 35,
16         62, 54, 46, 38, 30, 22, 14,
17         6, 61, 53, 45, 37, 29, 21,
18         13,  5, 60, 52, 44, 36, 28,
19         20, 12,  4, 27, 19, 11,  3
20             ]
21
22 # number left rotations of pc1
23 # 每轮循环左移位数
24 __left_rotations = [
25         1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1
26     ]
27
28 # permuted choice key (table 2)
29 # 压缩置换
30 __pc2 = [
31     13, 16, 10, 23,  0,  4,
32      2, 27, 14,  5, 20,  9,
33     22, 18, 11,  3, 25,  7,
34     15,  6, 26, 19, 12,  1,
35     40, 51, 30, 36, 46, 54,
36     29, 39, 50, 44, 32, 47,
37     43, 48, 38, 55, 33, 52,
38     45, 41, 49, 35, 28, 31
39     ]
40
41 # initial permutation IP
42 # 初始置换IP
43 __ip = [57, 49, 41, 33, 25, 17, 9,  1,
44         59, 51, 43, 35, 27, 19, 11, 3,
45     61, 53, 45, 37, 29, 21, 13, 5,
46     63, 55, 47, 39, 31, 23, 15, 7,
47     56, 48, 40, 32, 24, 16, 8,  0,
48     58, 50, 42, 34, 26, 18, 10, 2,
49     60, 52, 44, 36, 28, 20, 12, 4,
50     62, 54, 46, 38, 30, 22, 14, 6
51     ]
52
53 # Expansion table for turning 32 bit blocks into 48 bits
54 # 扩展变换
55 __expansion_table = [
56     31,  0,  1,  2,  3,  4,
57      3,  4,  5,  6,  7,  8,
58      7,  8,  9, 10, 11, 12,
59     11, 12, 13, 14, 15, 16,
60     15, 16, 17, 18, 19, 20,
61     19, 20, 21, 22, 23, 24,
62     23, 24, 25, 26, 27, 28,
63     27, 28, 29, 30, 31,  0
64         ]
65
66 # The (in)famous S-boxes
67 # S 盒
68 __sbox = [
69     # S1
70     [14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7,
71      0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8,
72      4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0,
73      15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13],
74
75     # S2
76     [15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10,
77      3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5,
78      0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15,
79      13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9],
80     # S3
81     [10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8,
82      13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1,
83      13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7,
84      1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12],
85
86     # S4
87     [7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15,
88      13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9,
89      10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4,
90      3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14],
91
92     # S5
93     [2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9,
94      14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6,
95      4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14,
96      11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3],
97
98     # S6
99     [12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11,
100     10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8,
101      9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6,
102      4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13],
103
104     # S7
105     [4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1,
106      13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6,
107      1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2,
108      6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12],
109
110     # S8
111     [13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7,
112      1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2,
113      7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8,
114      2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11],
115     ]
116
117
118 # 32-bit permutation function P used on the output of the S-boxes
119 # P-盒置换
120 __p = [
121     15, 6, 19, 20, 28, 11,
122     27, 16, 0, 14, 22, 25,
123     4, 17, 30, 9, 1, 7,
124     23,13, 31, 26, 2, 8,
125     18, 12, 29, 5, 21, 10,
126     3, 24
127     ]
128
129 # final permutation IP^-1
130 # 末尾置换IP^-1
131 __fp = [
132     39,  7, 47, 15, 55, 23, 63, 31,
133     38,  6, 46, 14, 54, 22, 62, 30,
134     37,  5, 45, 13, 53, 21, 61, 29,
135     36,  4, 44, 12, 52, 20, 60, 28,
136     35,  3, 43, 11, 51, 19, 59, 27,
137     34,  2, 42, 10, 50, 18, 58, 26,
138     33,  1, 41,  9, 49, 17, 57, 25,
139     32,  0, 40,  8, 48, 16, 56, 24
140     ]
141 def __String_to_BitList(data):
142     """Turn the string data,into a list of bits"""
143     data = [ord(c) for c in data] #转换成十进制数
144     sl = len(data)*8
145     pos = 0
146     result = [0]*sl #共有 sl 位
147     for ch in data:
148         i = 7
149         while i>=0:
150             if ch & (1