C++实现DES加密算法实例解析
本文所述实例是一个实现DES加密算法的程序代码，在C++中，DES加密是比较常用的加密算法了，且应用非常广泛。本CPP类文件可满足你的DES加密需要，代码中附带了丰富的注释，相信对于大家理解DES可以起到很大的帮助。
具体实现代码如下：
#include"memory.h"
#include"stdio.h"
enum{encrypt,decrypt};//ENCRYPT:加密，DECRYPT：解密
voiddes_run(charout[8],charin[8],booltype=encrypt);
//设置密钥
voiddes_setkey(constcharkey[8]);
staticvoidf_func(boolin[32],constboolki[48]);//f函数
staticvoids_func(boolout[32],constboolin[48]);//s盒代替
//变换
staticvoidtransform(bool*out,bool*in,constchar*table,intlen);
staticvoidxor(bool*ina,constbool*inb,intlen);//异或
staticvoidrotatel(bool*in,intlen,intloop);//循环左移
//字节组转换成位组
staticvoidbytetobit(bool*out,constchar*in,intbits);
//位组转换成字节组
staticvoidbittobyte(char*out,constbool*in,intbits);
//置换IP表
conststaticcharip_table[64]={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};
//逆置换IP-1表
conststaticcharipr_table[64]={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位选择表
staticconstchare_table[48]={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换位表
conststaticcharp_table[32]={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};
//pc1选位表
conststaticcharpc1_table[56]={
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
};
//pc2选位表
conststaticcharpc2_table[48]={
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
};
//左移位数表
conststaticcharloop_table[16]={1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1};
//S盒
conststaticchars_box[8][4][16]={
//s1
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,
//s2
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,
//s3
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,
//s4
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,
//s5
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,
//s6
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,
//s7
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,
//s8
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
};
staticboolsubkey[16][48];//16圈子密钥
voiddes_run(charout[8],charin[8],booltype)
{
staticboolm[64],tmp[32],*li=&m[0],*ri=&m[32];
bytetobit(m,in,64);
transform(m,m,ip_table,64);
if(type==encrypt){
for(inti=0;i<16;i++){
memcpy(tmp,ri,32);
f_func(ri,subkey[i]);
xor(ri,li,32);
memcpy(li,tmp,32);
}
}else{
for(inti=15;i>=0;i--){
memcpy(tmp,li,32);
f_func(li,subkey[i]);
xor(li,ri,32);
memcpy(ri,tmp,32);
}
}
transform(m,m,ipr_table,64);
bittobyte(out,m,64);
}
voiddes_setkey(constcharkey[8])
{
staticboolk[64],*kl=&k[0],*kr=&k[28];
bytetobit(k,key,64);
transform(k,k,pc1_table,56);
for(inti=0;i<16;i++)
{
rotatel(kl,28,loop_table[i]);
rotatel(kr,28,loop_table[i]);
transform(subkey[i],k,pc2_table,48);
}
}
voidf_func(boolin[32],constboolki[48])
{
staticboolmr[48];
transform(mr,in,e_table,48);
xor(mr,ki,48);
s_func(in,mr);
transform(in,in,p_table,32);
}
voids_func(boolout[32],constboolin[48])
{
for(chari=0,j,k;i<8;i++,in+=6,out+=4)
{
j=(in[0]<<1)+in[5];
k=(in[1]<<3)+(in[2]<<2)+(in[3]<<1)+in[4];
bytetobit(out,&s_box[i][j][k],4);
}
}
voidtransform(bool*out,bool*in,constchar*table,intlen)
{
staticbooltmp[256];
for(inti=0;i<len;i++)
tmp[i]=in[table[i]-1];
memcpy(out,tmp,len);
}
voidxor(bool*ina,constbool*inb,intlen)
{
for(inti=0;i<len;i++)
ina[i]^=inb[i];
}
voidrotatel(bool*in,intlen,intloop)
{
staticbooltmp[256];
memcpy(tmp,in,loop);
memcpy(in,in+loop,len-loop);
memcpy(in+len-loop,tmp,loop);
}
voidbytetobit(bool*out,constchar*in,intbits)
{
for(inti=0;i<bits;i++)
out[i]=(in[i/8]>>(i%8))&1;
}
voidbittobyte(char*out,constbool*in,intbits)
{
memset(out,0,(bits+7)/8);
for(inti=0;i<bits;i++)
out[i/8]|=in[i]<<(i%8);
}
voidmain()
{
charkey[8]={'p','r','o','g','r','a','m'},str[8];
puts("*****************DES***********************");
printf("\n");
printf("\n");
puts("pleaseinputyourwords");
gets(str);
printf("\n");
puts("****************************************");
des_setkey(key);
des_run(str,str,encrypt);
puts("afterencrypting:");
puts(str);
printf("\n");
puts("****************************************");
puts("afterdecrypting:");
des_run(str,str,decrypt);
puts(str);
printf("\n");
puts("****************************************");
printf("\n");
}
感兴趣的朋友可以测试运行一下本文实例，相信能够对大家的C++程序开发起到一定的帮助作用。