引例：DES 加密
5.1 此题给出了一轮DES加密的例子，假设明文和密文都是：
00000001 00100011 01000101 01100111 10001001 10101011 11001101 11101111
解题思路
答案见如下代码结果
python 实现
#DES的Python实现--若初·知乎
import binascii
K=[0,0,0,0,
0,0,0,0,
0,0,0,0,
0,0,0,0]
def str_to_hex(string): #Unicode字符串转16进制字符串
hex_string=''
for i in string:
hex_string=hex_string + '%02x'%ord(i)
return hex_string
def hex_to_bin(string): #16进制字符串转2进制字符串
hex_to_bin_table=('0000','0001','0010','0011','0100','0101','0110','0111','1000','1001','1010','1011','1100','1101','1110','1111')
bin_string=''
for i in string:
i=int(i,16)
bin_string=bin_string + hex_to_bin_table[i]
return bin_string
def bin_to_hex(string): #2进制字符串转16进制字符串
changed_str=''
while(len(string)>0):
temp=string[:4]
temp=int(temp, 2)
changed_str=changed_str + '%0x'%temp
string=string[4:]
return changed_str
def permutation1(key): #置换选择1
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)
changed_key=''
for i in range(56):
changed_key = changed_key + key[pc1[i]-1]
return changed_key
def permutation2(C, D): #置换选择2
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)
key = C + D
changed_key=''
for i in range(48):
changed_key = changed_key + key[pc2[i]-1]
return changed_key
def ROL(string, i): #循环左移
changed_string=''
if(i==1):
changed_string=string[1:] + string[:1]
if(i==2):
changed_string=string[2:] + string[:2]
return changed_string
def permutation_IP(code): #置换选择IP
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)
changed_code=''
for i in range(64):
changed_code+=code[ip[i]-1]
return changed_code
def permutation_IP_1(code): #置换选择IP逆
ip_1=(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)
changed_code=''
for i in range(64):
changed_code+=code[ip_1[i]-1]
return changed_code
def E(code): #选择运算E
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_list=''
for i in range(48):
return_list=return_list + code[e[i]-1]
return return_list
def S(code): #选择运算S
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]]]
return_list=''
for i in range(8):
row=int(str(code[i*6])+str(code[i*6+5]),2)#选择行
raw=int(str(code[i*6+1])+str(code[i*6+2])+str(code[i*6+3])+str(code[i*6+4]),2)#选择列
return_list=return_list + '%0x'%s[i][row][raw]
#选择一个数，并转换为16进制数
return_list=hex_to_bin(return_list)
#整个转换为2进制字符串
return return_list
def permutation_P(code):#置换选择P
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_list=''
for i in range(32):
return_list=return_list + code[p[i]-1]
return return_list
def f(A,i): #加密函数f
global K
result=E(A)
if i==0:
print('E(R0)',result)
result=int(result,2)
result=result ^ int(K[i],2)
result='%0x'%result
result=hex_to_bin(result)
result=(48-len(result))*'0' + result#增长到48位
if i==0:
print("A: ",result)
result=S(result)
if i==0:
print("B: ",result)
result=permutation_P(result)
if i==0:
print("P(B): ",result)
return result
def gen_K(key):
global K
ROL_table=(1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1)
key=permutation1(key)
C=[]
D=[]
C.append(key[:28])
D.append(key[28:])
for i in range(16):
C.append(ROL(C[i],ROL_table[i]))
D.append(ROL(D[i],ROL_table[i]))
K[i]=permutation2(C[i+1],D[i+1])
def DES_encrypt(plaintext):#总体加密结构
result=''
result=permutation_IP(plaintext)
L=[]
R=[]
L.append(result[0:32])
R.append(result[32:64])
for i in range(16):
L.append(R[i])
temp=hex_to_bin('%0x'%(int(f(R[i],i),2) ^ int(L[i],2)))
temp=(32-len(temp))*'0' + temp#增加到32位，前面全用0填满
R.append(temp)
if i==0:
print('L: ',L)
print('R: ',R)
#print('E(R0): ',f(R[i],i))
result=R[16]+L[16]
result=permutation_IP_1(result)
result=bin_to_hex(result)#16进制ASCII码
#result=str.encode(result)
#print(binascii.a2b_hex(result))
print('result in hex:' + result)
choose=input('choose 1 for encode, 2 for decode: ')
if choose=='1': #encode
#debug用
key_64bits='0000000'+'0010001'+'0100010'+'0110011'+'1000100'+'1010101'+'1100110'+'1110111'
plaintext ='00000001'+'00100011'+'01000101'+'01100111'+'10001001'+'10101011'+'11001101'+'11101111'
'''
#key=input('input the key(56bits, 7words): ')#密钥
while(len(key)!=7):
key=input('input the key(56bits, 7words): ')
plaintext=input('input the plaintext: ')#明文
#print(len(hex_to_bin(str_to_hex(plaintext))))
key_64bits=''
for i in key:#密钥转成2进制字符串
key_64bits=key_64bits + hex_to_bin('%02x'%ord(i))
'''
key_64bits=key_64bits[0:7] + '0' + key_64bits[7:14] + '0' + key_64bits[14:21] + '0' + key_64bits[21:28] + '0' + key_64bits[28:35] + '0' + key_64bits[35:42] + '0' + key_64bits[42:49] + '0' + key_64bits[49:56] + '0'
#56位密钥扩展成64位
#print('length of the key:' + str(len(key_64bits)))
#plaintext=str_to_hex(plaintext)
#plaintext=hex_to_bin(plaintext)
#明文转2进制字符串
gen_K(key_64bits)
print('K: ' + str(K))
while(len(plaintext)>=64):
plaintext_64bits=plaintext[:64]
DES_encrypt(plaintext_64bits)
plaintext=plaintext[64:]
if(len(plaintext)!=0):
i=64-len(plaintext)
plaintext_64bits=plaintext + i*'0'
DES_encrypt(plaintext_64bits)
if choose=='2': #decode
key='1234567'
#key=input('input the key(56bits, 7words): ')#密钥
while(len(key)!=7):
key=input('input the key(56bits, 7words): ')
ciphertext=input('input the ciphertext: ')#密文
key_64bits=''
for i in key:#密钥转成2进制字符串
key_64bits=key_64bits + hex_to_bin('%02x'%ord(i))
key_64bits=key_64bits[0:7] + '0' + key_64bits[7:14] + '0' + key_64bits[14:21] + '0' + key_64bits[21:28] + '0' + key_64bits[28:35] + '0' + key_64bits[35:42] + '0' + key_64bits[42:49] + '0' + key_64bits[49:56] + '0'
#56位密钥扩展成64位
#print('length of the key:' + str(len(key_64bits)))
ciphertext = str_to_hex(ciphertext)
ciphertext = hex_to_bin(ciphertext)
gen_K(key_64bits)
K.reverse()
while(len(ciphertext)>=64):
ciphertext_64bits=ciphertext[:64]
DES_encrypt(ciphertext_64bits)
ciphertext=ciphertext[64:]
if(len(ciphertext)!=0):
i=64-len(ciphertext)
ciphertext_64bits=ciphertext + i*'0'
DES_encrypt(ciphertext_64bits)
# choose 1 for encode, 2 for decode: 1
# K: ['000010110000001001100111100110110100100110100101', '011010011010011001011001001001010110101000100110', '010001011101010010001010101101000010100011010010', '011100101000100111010010101001011000001001010111', '001111001110100000000011000101111010011011000010', '001000110010010100011110001111001000010101000101', '011011000000010010010101000010101110010011000110', '010101111000100000111000011011001110010110000001', '110000001100100111101001001001101011100000111001', '100100011110001100000111011000110001110101110010', '001000010001111110000011000011011000100100111010', '011100010011000011100101010001010101110001010100', '100100011100010011010000010010011000000011111100', '010101000100001110110110100000011101110010001101', '101101101001000100000101000010100001011010110101', '110010100011110100000011101110000111000000110010']
# E(R0) 011110100001010101010101011110100001010101010101
# A: 011100010001011100110010111000010101110011110000
# B: 00001100001000010110110101010000
# P(B): 10010010000111000010000010011100
# L: ['11001100000000001100110011111111', '11110000101010101111000010101010']
# R: ['11110000101010101111000010101010', '01011110000111001110110001100011']
# result in hex:56cc09e7cfdc4cef