要求是实现DES加密，解密，我是用python实现的，还是有挺多坑的，改bug就改了挺久，加密实现后，解密过程就比较轻松。
另外，附加base64编码源码
要求：输入秘钥为64位二进制数（有效位为56位，其中每八位最后一位为奇偶校验位），明文为64位二进制数，输出为64位二进制数，解密过程大致为逆向过程
base64代码如下：
base='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
def base64(string):
out=''
c=len(string)%3
a=''.join(bin(ord(i)).replace('0b','').zfill(8) for i in string)
if(c==1):
a+='0000'
if(c==2):
a+='00'
m=int(len(a)/6)
for j in range(m):
out+=base[int(a[j*6:j*6+6],2)]
if(c==1):
out+='=='
if(c==2):
out+='='
return out
string=raw_input('please input the text:')
print ('the base64text is:'),base64(string)
DES代码如下：
# -*- coding: utf-8 -*-
import time
import base64
import os
m=0
C0=''
D0=''
L0=''
R0=''
cipher=''
outtext=''
substitute1=[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]
substitute2=[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]
shift=[1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1]
KEY=[ dict() for i in range(16)]
sbox= [
[
0xe,0x4,0xd,0x1,0x2,0xf,0xb,0x8,0x3,0xa,0x6,0xc,0x5,0x9,0x0,0x7,
0x0,0xf,0x7,0x4,0xe,0x2,0xd,0x1,0xa,0x6,0xc,0xb,0x9,0x5,0x3,0x8,
0x4,0x1,0xe,0x8,0xd,0x6,0x2,0xb,0xf,0xc,0x9,0x7,0x3,0xa,0x5,0x0,
0xf,0xc,0x8,0x2,0x4,0x9,0x1,0x7,0x5,0xb,0x3,0xe,0xa,0x0,0x6,0xd,
],
[
0xf,0x1,0x8,0xe,0x6,0xb,0x3,0x4,0x9,0x7,0x2,0xd,0xc,0x0,0x5,0xa,
0x3,0xd,0x4,0x7,0xf,0x2,0x8,0xe,0xc,0x0,0x1,0xa,0x6,0x9,0xb,0x5,
0x0,0xe,0x7,0xb,0xa,0x4,0xd,0x1,0x5,0x8,0xc,0x6,0x9,0x3,0x2,0xf,
0xd,0x8,0xa,0x1,0x3,0xf,0x4,0x2,0xb,0x6,0x7,0xc,0x0,0x5,0xe,0x9,
],
[
0xa,0x0,0x9,0xe,0x6,0x3,0xf,0x5,0x1,0xd,0xc,0x7,0xb,0x4,0x2,0x8,
0xd,0x7,0x0,0x9,0x3,0x4,0x6,0xa,0x2,0x8,0x5,0xe,0xc,0xb,0xf,0x1,
0xd,0x6,0x4,0x9,0x8,0xf,0x3,0x0,0xb,0x1,0x2,0xc,0x5,0xa,0xe,0x7,
0x1,0xa,0xd,0x0,0x6,0x9,0x8,0x7,0x4,0xf,0xe,0x3,0xb,0x5,0x2,0xc,
],
[
0x7,0xd,0xe,0x3,0x0,0x6,0x9,0xa,0x1,0x2,0x8,0x5,0xb,0xc,0x4,0xf,
0xd,0x8,0xb,0x5,0x6,0xf,0x0,0x3,0x4,0x7,0x2,0xc,0x1,0xa,0xe,0x9,
0xa,0x6,0x9,0x0,0xc,0xb,0x7,0xd,0xf,0x1,0x3,0xe,0x5,0x2,0x8,0x4,
0x3,0xf,0x0,0x6,0xa,0x1,0xd,0x8,0x9,0x4,0x5,0xb,0xc,0x7,0x2,0xe,
],
[
0x2,0xc,0x4,0x1,0x7,0xa,0xb,0x6,0x8,0x5,0x3,0xf,0xd,0x0,0xe,0x9,
0xe,0xb,0x2,0xc,0x4,0x7,0xd,0x1,0x5,0x0,0xf,0xa,0x3,0x9,0x8,0x6,
0x4,0x2,0x1,0xb,0xa,0xd,0x7,0x8,0xf,0x9,0xc,0x5,0x6,0x3,0x0,0xe,
0xb,0x8,0xc,0x7,0x1,0xe,0x2,0xd,0x6,0xf,0x0,0x9,0xa,0x4,0x5,0x3,
],
[
0xc,0x1,0xa,0xf,0x9,0x2,0x6,0x8,0x0,0xd,0x3,0x4,0xe,0x7,0x5,0xb,
0xa,0xf,0x4,0x2,0x7,0xc,0x9,0x5,0x6,0x1,0xd,0xe,0x0,0xb,0x3,0x8,
0x9,0xe,0xf,0x5,0x2,0x8,0xc,0x3,0x7,0x0,0x4,0xa,0x1,0xd,0xb,0x6,
0x4,0x3,0x2,0xc,0x9,0x5,0xf,0xa,0xb,0xe,0x1,0x7,0x6,0x0,0x8,0xd,
],
[
0x4,0xb,0x2,0xe,0xf,0x0,0x8,0xd,0x3,0xc,0x9,0x7,0x5,0xa,0x6,0x1,
0xd,0x0,0xb,0x7,0x4,0x9,0x1,0xa,0xe,0x3,0x5,0xc,0x2,0xf,0x8,0x6,
0x1,0x4,0xb,0xd,0xc,0x3,0x7,0xe,0xa,0xf,0x6,0x8,0x0,0x5,0x9,0x2,
0x6,0xb,0xd,0x8,0x1,0x4,0xa,0x7,0x9,0x5,0x0,0xf,0xe,0x2,0x3,0xc,
],
[
0xd,0x2,0x8,0x4,0x6,0xf,0xb,0x1,0xa,0x9,0x3,0xe,0x5,0x0,0xc,0x7,
0x1,0xf,0xd,0x8,0xa,0x3,0x7,0x4,0xc,0x5,0x6,0xb,0x0,0xe,0x9,0x2,
0x7,0xb,0x4,0x1,0x9,0xc,0xe,0x2,0x0,0x6,0xa,0xd,0xf,0x3,0x5,0x8,
0x2,0x1,0xe,0x7,0x4,0xa,0x8,0xd,0xf,0xc,0x9,0x0,0x3,0x5,0x6,0xb,
]
]
substituteip= [
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]
selectoperate=[
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]
substituteP=[
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]
resubstituteip=[
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]
def handleraw(string):
a=''
for i in string:
a+=bin(ord(i)).replace('0b','').zfill(8)
return a
def shiftleft(string,x):
return string[-(len(string)-x):]+string[:x]
def encodepassword1(x):
global C0
global D0
for i in range(0,28):
C0+=x[substitute1[i]-1]
for j in range(28,56):
D0+=x[substitute1[j]-1]
k=0
def encodepassword2():
global k,C0,D0
t=''
if(k!=16):
C0=shiftleft(C0,shift[k])
D0=shiftleft(D0,shift[k])
s=C0+D0
for i in substitute2:
t+=s[i-1]
KEY[k]=t
k+=1
encodepassword2()
def substituteIP(string):
global L0,R0
a=''
for i in substituteip:
a+=string[i-1]
L0=a[:32]
R0=a[-32:]
def sboxoperate():
mid=''
for i in selectoperate:
mid+=R0[i-1]
mid=str(bin(int(mid,2)^int(KEY[m-1],2)).replace('0b','').zfill(48))
outraw=''
for n in range(8):
a=int(mid[6*n]+mid[6*n+5],2)
b=int(mid[(6*n+1):(6*n+5)],2)
outraw+=str(bin(int(str(sbox[n][a*16+b]),10)).replace('0b','').zfill(4))
'''print 'S:',m,outraw'''
out=''
for i in substituteP:
out+=outraw[i-1]
return out
def encodemain():
global m,L0,R0,cipher
'''print 'L0,R0',L0,R0'''
m+=1
a=L0
L0=R0
R0=str(bin(int(sboxoperate(),2)^int(a,2)).replace('0b','').zfill(32))
if(m!=16):
encodemain()
else:
b=R0+L0
'''print 'L0,R0',L0,R0'''
for i in resubstituteip:
cipher+=b[i-1]
def decodecircle():
global L0,R0,outtext,m
a=R0
R0=L0
L0=str(bin(int(sboxoperate(),2)^int(a,2)).replace('0b','').zfill(32))
m-=1
if(m!=0):
decodecircle()
else:
d=L0+R0
decodetext=[0 for i in range(64)]
for i in range(64):
decodetext[substituteip[i]-1]=d[i]
outtext=''.join(decodetext)
def decoderesubstituteip(string):
global R0,L0,m
m=16
a=[0 for i in range(64)]
for i in range(64):
a[resubstituteip[i]-1]=string[i]
a=''.join(a)
R0=a[:32]
L0=a[-32:]
if __name__=='__main__':
e=raw_input('This is a DES encrypt and decrypt function
press 1 to encrypt, 2 to decrypt:')
password=raw_input('please input the key:
')
encodepassword1(password)
encodepassword2()
'''print 'the KEY is:
',KEY'''
if(e=='1'):
text=raw_input('please input the text:
')
substituteIP(text)
encodemain()
print 'the cipher is:',cipher
if(e=='2'):
ciphertext=raw_input('please input the cipher:
')
decoderesubstituteip(ciphertext)
decodecircle()
print 'the decodetext is:',outtext
os.system("pause")