DES加密解密（C++实现）

这是我们信安协会很早布置的作业，前几天终于写完了，嘿嘿O(∩_∩)O~

其实DES加密很简单，流程如下

1.对64位明文进行初置换，结果为A

2.将A分为两部分，左32位记为L，右32位记为R

3.对R进行拓展置换，得到X（48位）

4.将第I轮的密钥与X异或，得到Y（48位）

5.将Y穿入S盒，得到Z（32位）

6.将Z与L异或，结果传入L中

7.交换R和L

8.再次重复2~7,共计16次

9.将L和R整合，并将结果做末置换，加密完成

解密的流程其实是一样的额，只不过密钥不一样

假设加密时第i轮用的密钥Ki，那么解密时第i轮用的密钥是K(17-i)

下面说一下密钥生成的过程：

首先，我们一开始输入的密钥为X（64位）

1.将密钥X做密钥置换，取出其中58位记为T(58位)

2.取T左边28位为L,T右边28位为R

3.分别对R，L作循环左移

4.再对其做扩展运算，得到K[i]

6.重复3~4,共16次

这样大概也就说清楚了

#include
#include
#include

#define BIT bool

using namespace std;

BIT K[16][48];

int 
    //初置换 
    IP[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},
    //末置换 
    FP[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},
    //密钥置换 
    KP[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},
    //密钥位移 
    KM[16] = {
     1 ,  1 ,  2 ,  2 ,  2 ,  2 ,  2 ,  2 , 
     1 ,  2 ,  2 ,  2 ,  2 ,  2 ,  2 ,  1},
    //压缩置换 
    CP[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},
    //扩展置换 
    EP[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},
    //S盒 
    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}}},
    //P盒
    PP[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}; 

void Initial_Permutation(BIT pt[64])
{
     BIT tmp[64];
     for(int i = 0;i < 64;i++)
             tmp[i] = pt[IP[i]-1];
     memcpy(pt,tmp,sizeof(tmp));
     return ;
}

void Final_Permutation(BIT pt[64])
{
     BIT tmp[64];
     for(int i = 0;i < 64;i++)
             tmp[i] = pt[FP[i]-1];
     memcpy(pt,tmp,sizeof(tmp));
     return ;
}

void P_Box_Permutation(BIT x[32])
{
     BIT tmp[32];
     for(int i = 0;i < 32;i++)
             tmp[i] = x[PP[i]-1];
     memcpy(x,tmp,sizeof(tmp));
     return ;     
}
     
void Generate_K(BIT SK[64])
{
     BIT L[60],R[60];
     int i,j,st;
     
     memset(K,0,sizeof(K));

     for(i = 0;i < 28;i++)
             L[i+28] = L[i] = SK[KP[i]-1],
             R[i+28] = R[i] = SK[KP[i+28]-1];
     st = 0;
     for(i = 0;i < 16;i++) {
             st += KM[i];
             for(j = 0;j < 48;j++)
                     K[i][j] = (CP[j] < 28)?L[CP[j] + st - 1]:R[CP[j] - 29 + st];
     	     }
     return ;
}

void Work(BIT L[32],BIT R[32],BIT KEY[48],int cnt)
{
     BIT X[48],RES[32];
     memset(RES,0,sizeof(RES));
     memset(X,0,sizeof(X));
     int i,j,a,b,st,st2,tmp;
     
     for(i = 0;i < 48;i++)
          X[i] = R[EP[i]-1] ^ KEY[i];
        
     for(i = 0;i < 8;i++) {
 
           st = i * 6;
           a = (X[st] << 1) + X[st + 5];
           b = (X[st + 1] << 3) + (X[st + 2] << 2) + (X[st + 3] << 1) + X[st + 4]; 
           tmp = S_box[i][a][b];
           st2 = i * 4;
           for(j = 0;j < 4;j++)
                 RES[st2 + (3 - j)] |= (tmp >> j)&1;
           }

      P_Box_Permutation(RES);
      
      for(i = 0;i < 32;i++)
            L[i] ^= RES[i];

      if (cnt == 15) return ;

      BIT temp[32];
	
      memcpy(temp,L,sizeof(temp));
      memcpy(L,R,sizeof(temp));
      memcpy(R,temp,sizeof(temp));
      
      return ;  
}

void DES_enc(char txt[10],char enc[10])
{
     int i,j;
     BIT L[32],R[32];
     BIT pt[64];

     for(i = 0;i < 8;i++)
          for(j = 7;j >= 0;j--)
                pt[i * 8 + (7 - j)] = (txt[i] >> j) & 1;

     Initial_Permutation(pt);

     for(i = 0;i < 32;i++)
           L[i] = pt[i],R[i] = pt[i + 32];

     for(i = 0;i < 16;i++)
           Work(L,R,K[i],i);

     for(i = 0;i < 32;i++)
           pt[i] = L[i],pt[i + 32] = R[i];
           
    
     Final_Permutation(pt);

     for(i = 0;i < 8;i++)
           for(j = 7;j >= 0;j--)
                 enc[i] |= pt[i * 8 + (7 - j)] << j;  

     return ;            
}

void DES_dec(char txt[10],char dec[10])
{
     int i,j;
     BIT L[32],R[32];
     BIT pt[64];
     
     for(i = 0;i < 8;i++)
          for(j = 7;j >= 0;j--)
                pt[i * 8 + (7 - j)] = (txt[i] >> j) & 1;

     Initial_Permutation(pt);

     for(i = 0;i < 32;i++)
           L[i] = pt[i],R[i] = pt[i + 32];

     for(i = 0;i < 16;i++)
           Work(L,R,K[15 - i],i);

     for(i = 0;i < 32;i++)
           pt[i] = L[i],pt[i + 32] = R[i];
           
     Final_Permutation(pt);
     
     for(i = 0;i < 8;i++)
           for(j = 7;j >= 0;j--)
                 dec[i] |= pt[i * 8 + (7 - j)] << j;  

     return ;            
}  

void DES_E()
{
     int tmp,i,j;
     BIT sk[64];
     char txt[10],key[10],res[10];
     char Fpt[100],Fct[100];
     FILE *P,*O;

     printf("Plase enter the plaintext file:");
     scanf("%s",Fpt);
     printf("Plase enter the key(8char):");
     scanf("%s",key);
     printf("Plase enter the ciphertext file:");
     scanf("%s",Fct);
     
     for(i = 0;i < 8;i++)
          for(j = 7;j >= 0;j--)
                sk[i * 8 + (7 - j)] = (key[i] >> j) & 1;     
          
     Generate_K(sk);
     
     P = fopen(Fpt,"r");
     O = fopen(Fct,"w");
     while(tmp = fread(txt,sizeof(txt[0]),8,P)) {
	   for(i = tmp;i < 8;i++) txt[i] = 0;
           memset(res,0,sizeof(res));
	   DES_enc(txt,res);
           fwrite(res,sizeof(res[0]),8,O);
           }
     fclose(O);
     fclose(P);
     return ;
}

void DES_D()
{
     int tmp,i,j;
     BIT sk[64];
     char txt[10],key[10],res[10];
     char Fpt[100],Fct[100];
     FILE *P,*O;

     printf("Plase enter the ciphertext file:");
     scanf("%s",Fpt);
     printf("Plase enter the key(8char):");
     scanf("%s",key);
     printf("Plase enter the plaintext file:");
     scanf("%s",Fct);

     for(i = 0;i < 8;i++)
          for(j = 7;j >= 0;j--)
                sk[i * 8 + (7 - j)] = (key[i] >> j) & 1;     
          
     Generate_K(sk);

     P = fopen(Fpt,"r");
     O = fopen(Fct,"w");
     while (tmp = fread(txt,sizeof(txt[0]),8,P)) {
	   for(i = tmp;i < 8;i++) txt[i] = 0;
           memset(res,0,sizeof(res));
	   DES_dec(txt,res);
           fwrite(res,sizeof(res[0]),8,O);
           }
     fclose(O);
     fclose(P);
     return ;
}

int main()
{
    char str[10];
    while(1){
             printf("Choice Mode{DEC(D) or ENC(E)}:");
             scanf("%s",str);
             if (str[0] == 'D') DES_D();
             else if (str[0] == 'E') DES_E();
             else return 0;            
             printf("OK...O^_^O\n");
    	     }
}