DES：对64位的明文分组进行操作。通过一个初始置换，将明文分组分成左半部分和右半部分，各32位长。然后进行16轮完全相同的运算，这些运算被称为函数F，在运算过程中数据与密钥结合。经过16轮后，左、右半部分合在一起，经过一个末置换（初始置换的逆置换），这样该算法就完成了。
代码实现
import re
from DES_BOX import *
# 将明文转化为二进制
def str2bin(message):
res = ''
for i in message:
tmp = bin(ord(i))[2:] # 将每个字符转化成二进制
tmp = str('0' * (8 - len(tmp))) + tmp # 补齐8位
res += tmp
if len(res) % 64 != 0:
count = 64 - len(res) % 64 # 不够64位补充0
else:
count = 0
res += '0' * count
return res
# 将密钥转化为二进制
def key2bin(key):
res = ''
for i in key:
tmp = bin(ord(i))[2:] # 将每个字符转化成二进制
tmp = str('0' * (8 - len(tmp))) + tmp # 补齐8位
res += tmp
if len(res) < 64:
count = 64 - len(res) % 64 # 不够64位补充0
res += '0' * count
else:
res = res[:64]
return res
# IP盒处理
def ip_change(str_bin):
res = ''
for i in IP_table:
res += str_bin[i - 1]
return res
# 生成子密钥
def gen_key(bin_key):
key_list = []
key1 = change_key1(bin_key) # 秘钥的PC-1置换
key_C0 = key1[0:28]
key_D0 = key1[28:]
for i in SHIFT: # shift左移位数
key_c = key_C0[i:] + key_C0[:i] # 左移操作
key_d = key_D0[i:] + key_D0[:i]
key_output = change_key2(key_c + key_d) # 秘钥的PC-2置换
key_list.append(key_output)
return key_list
# 秘钥的PC-1置换
def change_key1(my_key):
res = ""
for i in PC_1: # PC_1盒上的元素表示位置 只循环64次
res += my_key[i - 1] # 将密钥按照PC_1的位置顺序排列，
return res
# 秘钥的PC-2置换
def change_key2(my_key):
res = ""
for i in PC_2:
res += my_key[i - 1]
return res
# E盒置换
def e_change(str_left):
res = ""
for i in E:
res += str_left[i - 1]
return res
def xor_change(str1, str2):
res = ""
for i in range(0, len(str1)):
xor_res = int(str1[i], 10) ^ int(str2[i], 10) # 进行xor操作
if xor_res == 1:
res += '1'
if xor_res == 0:
res += '0'
return res
def s_change(my_str):
res = ""
c = 0
for i in range(0, len(my_str), 6): # 步长为6 表示分6为一组
now_str = my_str[i:i + 6] # 第i个分组
row = int(now_str[0] + now_str[5], 2) # 第r行
col = int(now_str[1:5], 2) # 第c列
# 第几个s盒的第row*16+col个位置的元素
num = bin(S[c][row * 16 + col])[2:] # 利用了bin输出有可能不是4位str类型的值，所以才有下面的循环并且加上字符0
for gz in range(0, 4 - len(num)): # 补全4位
num = '0' + num
res += num
c += 1
return res
def p_change(bin_str):
res = ""
for i in P:
res += bin_str[i - 1]
return res
def f(str_left, key):
e_change_output = e_change(str_left) # E扩展置换
xor_output = xor_change(e_change_output, key) # 将48位结果与子密钥Ki进行异或（xor）
s_change_output = s_change(xor_output)
res = p_change(s_change_output)
return res
# IP逆盒处理
def ip_re_change(bin_str):
res = ""
for i in IP_re_table:
res += bin_str[i - 1]
return res
# 二进制转字符串
def bin2str(bin_str):
res = ""
tmp = re.findall(r'.{8}', bin_str) # 每8位表示一个字符
for i in tmp:
res += chr(int(i, 2))
return res
import time
def encrypt():
bin_str = str2bin(input('请输入明文：'))
bin_key = key2bin(input('请输入密钥：'))
ss=0
for i in range(0,1000):
t1=time.time()
tmp = re.findall(r'.{64}', bin_str)
result = ''
for i in tmp:
str_bin = ip_change(i) # IP置换
key_lst = gen_key(bin_key) # 生成16个子密钥
str_left = str_bin[:32]
str_right = str_bin[32:]
for j in range(15): # 先循环15次 因为最后一次不需要不用换位
f_res = f(str_right, key_lst[j])
str_left = xor_change(f_res, str_left)
str_left, str_right = str_right, str_left
f_res = f(str_right, key_lst[15]) # 第16次
str_left = xor_change(str_left, f_res)
fin_str = ip_re_change(str_left + str_right) # ip的逆
result += fin_str
last = bin2str(result)
t2 = time.time()
s=t2-t1
ss=ss+s
print(ss/1000)
print('密文为:', last)
open('secret.txt', 'w', encoding="utf-8").write(last)
print('密文已经保存到secret.txt中')
def decrypt(): # 解密和加密的步骤差不多，但要注意解密时密钥是倒过来的 ，第一个的时候左右不交换
bin_str = str2bin(input('请输入密文（直接回车会自动读取secret.txt中的密文）：') or open('secret.txt', encoding="utf-8").read())
bin_key = key2bin(input('请输入密钥：'))
tmp = re.findall(r'.{64}', bin_str)
result = ''
for i in tmp:
str_bin = ip_change(i) # IP置换
key_lst = gen_key(bin_key) # 生成16个子密钥
str_left = str_bin[:32]
str_right = str_bin[32:]
for _j in range(1, 16):
j = 16 - _j # 解密的时候秘钥反过来的
f_res = f(str_right, key_lst[j])
str_left = xor_change(f_res, str_left)
str_left, str_right = str_right, str_left
f_res = f(str_right, key_lst[0])
str_left = xor_change(str_left, f_res)
fin_str = ip_re_change(str_left + str_right) # ip的逆
result += fin_str
last = bin2str(result)
print('明文为:', last)
if __name__ == '__main__':
print("1.使用DES加密")
print("2.使用DES解密")
while True:
mode = input('请输入1或2：')
if mode == '1':
encrypt()
break
elif mode == '2':
decrypt()
break
else:
print('error')
调用的另外一个文件和from 后面的文件名相同
IP_table = [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]
IP_re_table = [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]
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]
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],
# key
PC_1 = [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]
PC_2 = [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]
# 秘钥左移的位数
SHIFT = [1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1]结果分析
实验心得：
DES是对称密钥加密和解密数据。DES还是一种分组加密算法，该算法每次处理固定长度的数据段。DES算法依赖于“混乱和扩散”的原则。混乱的目的是为隐藏任何明文同密文、或者密钥之间的关系，而扩散的目的是使明文中的有效位和密钥一起组成尽可能多的密文。两者结合到一起就使得安全性变得相对较高。DES算法具体通过对明文进行一系列的排列和替换操作来将其加密。实验的关键就是从给定的初始密钥中得到16个子密钥的函数。要加密一组明文，每个子密钥按照顺序（1-16）以一系列的位操作施加于数据上，每个子密钥一次，一共重复16次。每一次迭代称之为一轮。要对密文进行解密可以采用同样的步骤，只是子密钥是按照逆向的顺序（16-1）对密文进行处理。
遇到的问题：
定义密钥时字符串长度为4的倍数 不然在解密的时候会出现报异常 字符串长度问题
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