分组加密算法 DES

分组加密算法在加解密中十分常见，因其安全性高，计算速度快。常用的有DES、AES、IDEA和RC6等 。

由于DES的安全性存在争议，且56位的密钥太短（1997年RSA悬赏破解），现在使用的是3DES和AES（高级加密标准）。

下面说一说DES，数据加密标准（DES）是一个分组加密算法，也是对称加密算法，加解密的密钥一样。

DES采用Feistel结构设计，处理的明文分组为64位，有效密钥为56位，输出密文为64位，是具有16轮迭代的分组对称密码算法。

DES算法

 

/*
DES算法，明文分组为64位（不足64位时补0），有效密钥56位，输出密文64位，16轮迭代
由于没有保存长度信息，对于可能有填充部分，最后解密的明文最后一块可能会出现多余字符
本程序的位从右往左为0~63（）
*/

#include
#include
#include

unsigned char IP[64+1] = {
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,
63,55,47,39,31,23,15,7,0};

unsigned char IPRev[64+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,
33,1,41,9,49,17,57,25,0};

unsigned char EExt[48+1] = {
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,
28,29,30,31,32,1,0};

unsigned char S[8][64] ={
{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}};

unsigned char P[56+1] = {
16,7,20,21,29,12,28,17,
1,15,23,26,5,18,31,10,
2,8,24,14,32,27,3,9,
19,13,30,6,22,11,4,25,0};

unsigned char PC1[56+1] = {
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,
21,13,5,28,20,12,4,0};

unsigned char PC2[48+1] = {
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,
30,22,14,6,61,53,45,37,0};

unsigned char LS[16] = {
1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1};

FILE *fp;

unsigned long long Message;
int flag;
unsigned long long keys[16];

void getMessage(char mode);
unsigned long long Rep(unsigned char rp[],unsigned long long s);//置换
unsigned int SBoxC(unsigned long long x);
void GenKeys(char mode);

unsigned int L,R;
unsigned long long K;

int main(int argc, char *argv[])
{
    char mode;
    char filename[256];
    unsigned char key[10];
    mode = *argv[1];
    strcpy(filename,argv[2]);

    if(argc != 4)
    {
        printf("参数有错误！\n");
        exit(0);
    }
    if(strlen(argv[3])!=8)
    {
        printf("密钥长度不正确!");
        exit(0);
    }
    strcpy(key,argv[3]);
/*  printf("请选择操作方式：加密 e ,解密 d :  ");
    scanf("%c",&mode);
    printf("请输入文件名：");
    scanf("%s",filename);
    printf("请输入密钥(64bit)：");
    scanf("%s",key); */

//  printf("%s",filename);
//  system("pause");
    if((fp=fopen(filename,"rb")) == NULL)
    {
        printf("文件无法打开");
        exit(0);
    }

    int inc = 0;
    K = 0;
    for(inc = 0 ;inc < 8; inc++)
        K |= (((unsigned long long)key[inc])<<((7-inc)<<3));
#ifdef DEBUG
    printf(" K %016llx ",K);
#endif
    FILE *fpOut;
    char fileOut[200];
    if(mode == 'e')
        strcat(strcpy(fileOut,"ED\0"),filename);
    else
        strcat(strcpy(fileOut,"DD\0"),filename+2);
    fpOut= fopen(fileOut,"wb");
//  fseek(fp, 0, SEEK_END);
//  fgetpos(fp, &pos);
    flag = 1;//判断是否结束
    int T;

    GenKeys(mode);

    getMessage(mode);
    while(flag)
    {
        Message = Rep(IP,Message);
        L = Message>>32;
        R = Message;

        int i =0;
        for(i =0 ; i < 16; i++)
        {
            T = R;
            R = Rep(P,SBoxC(Rep(EExt,(unsigned long long)R)^keys[i]))^L;
            L = T;
        }
        Message = (((unsigned long long)R)<<32)|L;
        Message = Rep(IPRev,Message);
        if(mode == 'e')
            fwrite(&Message,1,8,fpOut);
        else
        {
        Message = (Message>>56)|((Message&0x00ff000000000000)>>40)|((Message&0x0000ff0000000000)>>24)|((Message&0x000000ff00000000)>>8)|
                (Message<<56)|((Message&0x000000000000ff00)<<40)|((Message&0x0000000000ff0000)<<24)|((Message&0x00000000ff000000)<<8);
            fwrite(&Message,1,8,fpOut);
        }

/*      for(i = 0 ; i < 8 ; i++)
        {
            int out =(Message&(0x00000000000000ff<<(i*8))>>(i*8));
            fwrite(&out,1,1,fpOut);
        }  */
        getMessage(mode);
    }

    fclose(fp);
    fclose(fpOut);
    return 0;
}

void getMessage(char mode)
{
    Message = 0;
    flag = fread((void *)&Message,1,8,fp);
//  printf(" flag = %d %d %d ",flag,feof(fp),ferror(fp));
    if(flag == 0)
    {
        return;
    }
#ifdef DEBUG
    printf("Mm %016llx ",Message);
#endif
    if(mode == 'e')
    Message = (Message>>56)|((Message&0x00ff000000000000)>>40)|((Message&0x0000ff0000000000)>>24)|((Message&0x000000ff00000000)>>8)|
                (Message<<56)|((Message&0x000000000000ff00)<<40)|((Message&0x0000000000ff0000)<<24)|((Message&0x00000000ff000000)<<8);
#ifdef DEBUG
    printf("Mess %016llx ",Message);
//  system("pause");
#endif
}

unsigned long long Rep(unsigned char rp[],unsigned long long s)//置换
{
#ifdef DEBUG
printf("in Rep  ");
#endif
    int i = 0;
    unsigned long long ans=0;
    unsigned long long con = 1;
    for(i = 0 ; i < strlen(rp); i++)
    {
        ans |= ((s&(con << (rp[i]-1)))>> (rp[i]-1))<
        #ifdef DEBUG
        printf("time= %d ans %016llx ",i,ans);
        #endif
//      system("pause");
    }
#ifdef DEBUG
printf(" Rep end ");
#endif
    return ans;
}

unsigned int SBoxC(unsigned long long x)
{
#ifdef DEBUG
printf("in Sbox  ");
#endif
    int i = 0 , ans = 0;
    unsigned long long con = 0x3f;
    int t1_6 = 0,tr=0,tc=0;
    for(i = 0; i < 8; i++ )
    {
#ifdef DEBUG
printf(" Sbox For Begin  ");
#endif
        t1_6 = (x & (con <<(i*6)))>>(i*6);
        tr = ((t1_6&(1<<5))>>4)|(t1_6&1);
        tc = (t1_6&0x1f)>>1;
        ans|=(S[7-i][(tr<<4)+tc])<<(i*4);

#ifdef DEBUG
        printf(" ii = %d %x ",i,ans);
        system("pause");
        printf(" Sbox For end  ");
#endif
    }
#ifdef DEBUG
printf(" Sbox end  ");
#endif
    return ans;
}

unsigned int C,D;
void GenKeys(char mode)
{
    unsigned long long con = 0x0fffffff;
    K = Rep(PC1,K);
    C = (K&(con<<28))>>28;
    D = K&con;
    int i;
    if(mode == 'e')
    {
        for(i = 0; i < 16; i++)
        {
            C = (C<>(32-LS[i]));
            D = (D<>(32-LS[i]));
            K = (C<<28)|D;
            keys[i] = Rep(PC2,K);
        }
    }
    else
    {
        for(i = 0; i < 16; i++)
        {
            C = (C<>(32-LS[i]));
            D = (D<>(32-LS[i]));
            K = (C<<28)|D;
            keys[15 - i] = Rep(PC2,K);
        }
    }
}

编译器使用的是MingwGcc编译器。