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 void des_run(char out[8],char in[8],bool type=encrypt); //设置密钥 void des_setkey(const char key[8]); static void f_func(bool in[32],const bool ki[48]);//f函数 static void s_func(bool out[32],const bool in[48]);//s盒代替 //变换 static void transform(bool *out, bool *in, const char *table, int len); static void xor(bool *ina, const bool *inb, int len);//异或 static void rotatel(bool *in, int len, int loop);//循环左移 //字节组转换成位组 static void bytetobit(bool *out,const char *in, int bits); //位组转换成字节组 static void bittobyte(char *out, const bool *in, int bits); //置换IP表 const static char ip_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 const static char ipr_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 static const char e_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 const static char p_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 const static char pc1_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 const static char pc2_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 const static char loop_table[16]={1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1}; //S盒 const static char s_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 }; static bool subkey[16][48];//16圈子密钥 void des_run(char out[8],char in[8], bool type) { static bool m[64],tmp[32],*li=&m[0], *ri=&m[32]; bytetobit(m,in,64); transform(m,m,ip_table,64); if(type==encrypt){ for(int i=0;i<16;i++){ memcpy(tmp,ri,32); f_func(ri,subkey[i]); xor(ri,li,32); memcpy(li,tmp,32); } }else{ for(int i=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); } void des_setkey(const char key[8]) { static bool k[64], *kl=&k[0], *kr=&k[28]; bytetobit(k,key,64); transform(k,k,pc1_table,56); for(int i=0;i<16;i++) { rotatel(kl,28,loop_table[i]); rotatel(kr,28,loop_table[i]); transform(subkey[i],k,pc2_table,48); } } void f_func(bool in[32],const bool ki[48]) { static bool mr[48]; transform(mr,in,e_table,48); xor(mr,ki,48); s_func(in,mr); transform(in,in,p_table,32); } void s_func(bool out[32],const bool in[48]) { for(char i=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); } } void transform(bool *out,bool *in,const char *table,int len) { static bool tmp[256]; for(int i=0;i<len;i++) tmp[i]=in[table[i]-1]; memcpy(out,tmp,len); } void xor(bool *ina,const bool *inb,int len) { for(int i=0;i<len;i++) ina[i]^=inb[i]; } void rotatel(bool *in,int len,int loop) { static bool tmp[256]; memcpy(tmp,in,loop); memcpy(in,in+loop,len-loop); memcpy(in+len-loop,tmp,loop); } void bytetobit(bool *out,const char *in,int bits) { for(int i=0;i<bits;i++) out[i]=(in[i/8]>>(i%8)) &1; } void bittobyte(char *out,const bool *in,int bits) { memset(out,0,(bits+7)/8); for(int i=0;i<bits;i++) out[i/8]|=in[i]<<(i%8); } void main() { char key[8]={'p','r','o','g','r','a','m'},str[8]; puts("*****************DES***********************"); printf("n"); printf("n"); puts("please input your words"); gets(str); printf("n"); puts("****************************************"); des_setkey(key); des_run(str,str,encrypt); puts("after encrypting:"); puts(str); printf("n"); puts("****************************************"); puts("after decrypting:"); 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。
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