对于 F 函数（Feistel网络 ）
# F函数，用于处理一个半块
def Feistel(a, subKey):
assert len(a) == 32
assert len(subKey) == 48
t = binXor(Expand(a), subKey) # expend是前后重叠一个的拓展 32to48
t = S(t) # S盒 高混淆度防止差分攻击
t = P(t) # P置换。让同一个S盒输出的4个bit在下一个回合的expend之后由四个不同的S盒处理
return t
from functools import reduce
import numpy as np
# 整数转二进制数组，指定位长 n，大端序
def int2bin(a, n):
assert 0<=n and a < 2**n
res = np.zeros(n, dtype = int)
for x in range(n):
res[n-x-1] = a % 2
a = a // 2
return res.tolist()
assert int2bin(0x1a, 10) == [0, 0, 0, 0, 0, 1, 1, 0, 1, 0]
# 二进制数组转整数，大端序
def bin2int(a):
return reduce(lambda x,y: x*2+y, a)
assert bin2int([0, 0, 0, 0, 0, 1, 1, 0, 1, 0]) == 0x1a
# 循环左移off位
def leftRotate(a, off):
return a[off:] + a[:off]
assert leftRotate([0, 1, 0, 1, 1], 2) == [0, 1, 1, 0, 1]
# 异或
def binXor(a, b):
assert len(a) == len(b)
return [x^y for x, y in zip(a, b)]
assert binXor([1, 1, 0, 1], [0, 1, 1, 0]) == [1, 0, 1, 1]
# 初始置换
def IP(a):
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]
return [a[x-1] for x in ip]
testM = [0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 1, 1, 0, 1, 0, 1, 0, 1, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1]
assert IP(testM) == [1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0]
# 最终置换
def FP(a):
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]
return [a[x-1] for x in fp]
# 选择置换1
# 从64位输入密钥中选择56位，分为左右两个28位半密钥
def PC1(key):
pc1_l = [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]
pc1_r = [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]
return [key[x-1] for x in pc1_l], [key[x-1] for x in pc1_r]
testKey = [0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1]
testL, testR = PC1(testKey)
assert testL + testR == [1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1]
# 选择置换2
# 从56位的密钥中选取48位子密钥
def PC2(key):
assert len(key) == 56
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]
return [key[x-1] for x in pc2]
# 子密钥生成算法，由一个64位主密钥导出16个48位子密钥
def keyGen(key):
assert len(key) == 64
l, r = PC1(key)
off = [1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1]
res = []
for x in range(16):
l = leftRotate(l, off[x])
r = leftRotate(r, off[x])
res.append(PC2(l + r))
return res
assert keyGen(testKey)[-1] == [1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 1, 1, 0, 1, 1, 0, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1]
# S盒变换，输入48位，输出32位
def S(a):
assert len(a) == 48
S_box = [[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]]
a = np.array(a, dtype=int).reshape(8, 6)
res = []
for i in range(8):
# 用 S_box[i] 处理6位a[i]，得到4位输出
p = a[i]
r = S_box[i][bin2int([p[0], p[5], p[1], p[2], p[3], p[4]])]
res.append(int2bin(r, 4))
res = np.array(res).flatten().tolist()
assert len(res) == 32
return res
# 扩张置换，将32位的半块扩展到48位
def Expand(a):
assert len(a) == 32
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]
return [a[x-1] for x in e]
# P置换
def P(a):
assert len(a) == 32
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]
return [a[x-1] for x in p]
# F函数，用于处理一个半块
def Feistel(a, subKey):
assert len(a) == 32
assert len(subKey) == 48
t = binXor(Expand(a), subKey)
t = S(t)
t = P(t)
return t
def goRound(l, r, subKey):
return r, binXor(l, Feistel(r, subKey))
def DES(plain, key, method):
subkeys = keyGen(int2bin(key, 64))
if method == 'decrypt':
subkeys = subkeys[::-1]
m = IP(int2bin(plain, 64))
l, r = np.array(m, dtype=int).reshape(2, -1).tolist()
for i in range(16):
l, r = goRound(l, r, subkeys[i])
return bin2int(FP(r + l))
print(hex(DES(0x11aabbccddeeff01, 0xcafababedeadbeaf, 'encrypt')))
# 0x2973a7e54ec730a3
print(hex(DES(0x2973a7e54ec730a3, 0xcafababedeadbeaf, 'decrypt')))
# 0x11aabbccddeeff01