| 这次贴个实用点的,DES密码算法.该密码算法应该说还是比较安全的.作为一般的个人使用相信没有什么大的问题.
只是由于对C语言以及算法的理解有限,该DES算法程序实现的加密解密效率较低,加密文本文件尚感觉不到,如果用来加密多媒体文件等较大的文件,就会觉得像老牛拉车了.
DES密码算法是一种块加密算法,也就是一次加密一定大小的块.标准DES一次加密64个bit,也就是8个字节.我实现的时候是使用unsigned char [8]这样的数组作为缓冲区,也即数组中的每一个bit都用到了,如果用unsigned char [64]这样的数组作为缓冲取,也就是数组中的每一个元素只代表一个 bit.这样会造成内存的浪费.
在做的时候还遇到了另外一个问题,因为DES是块加密算法,所以如果一个文件的大小不能整除8字节的时候,就会无法加密解密剩下的几个不足8字节的文件,当时考虑的方法是:计算文件大小能否被8byte整除,无论能与不能,都为其添加数个字节使其能被8整除,然后多加一个byte的数据用来保存刚才添加字节的数量.比如:文件为9byte,程序就为其添加7byte,然后再添加1byte,最后这1byte的值为7.
运行参数为:程序名 希望加密的文件路径 保存加密后的文件路径 密钥 E/D(E为加密,D为解密)
#include <stdio.h>#include <string.h>//此DES算法为CBC--密码分组链接模式//此DES算法的加解密效率约为56K每秒。int Crypt(char *sourcepath,char *destpath,char *inputkey,char *inputiv);int Decrypt(char *sourcepath,char *destpath,char *inputkey,char *inputiv);int is_InputKeyRight(char *inputkey);int Check(int argc,char **argv);int is_Sourcepathright(char *source_path);int is_Destpathright(char *dest_path);void IP(unsigned char *output,unsigned char *input);void IP1(unsigned char *output,unsigned char *input);unsigned char getbit(int n,unsigned char ch);int EP(unsigned char *EPplaintext,unsigned char *plaintext);int F(unsigned char *r,unsigned char *k,unsigned char *output);void P(unsigned char *output,unsigned char *input);void FK(unsigned char *l,unsigned char *r,unsigned char *sk,unsigned char *output);int PC1(unsigned char *cd,unsigned char *input);int PC2(unsigned char *output,unsigned char *input);int LS1(unsigned char *input);void GenerateSubkey(char sk[16][6],char *inputkey);void des(unsigned char *output,unsigned char *plaintext,unsigned char sk[16][6],int flag);
int main(int argc,char **argv){ if (Check(argc,argv)==0){ return -1; } if (argv[5][0]=='e'||argv[5][0]=='E'){ if(Crypt(argv[1],argv[2],argv[3],argv[4])) return 1; else return -1; } if (argv[5][0]=='d'||argv[5][0]=='D'){ if(Decrypt(argv[1],argv[2],argv[3],argv[4])) return 1; else return -1; } return -1;}
unsigned char getbit(int n,unsigned char ch)//0-8均可作为n的传递值{ if(n==0) n=8; if(((ch>>(8-n))&1)==1) return 1; else return 0;}
void IP(unsigned char *output,unsigned char *input)//output[8]{ unsigned char IPmap[]={ 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 }; int i=0; int j=0; int k=7; for(i=0;i<8;i++){ for(j=0;j<8;j++){ output[i]=output[i]+getbit(IPmap[j+i*8]%8,input[(IPmap[j+i*8]-1)/8]); if(k>0) output[i]=output[i]<<1; k--; } k=7; }}
void IP1(unsigned char *output,unsigned char *input){ unsigned char IP1map[]={ 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 }; int i; int j; int k=7; for(i=0;i<8;i++){ for(j=0;j<8;j++){ output[i]=output[i]+getbit(IP1map[j+i*8]%8,input[(IP1map[j+i*8]-1)/8]); if(k>0) output[i]=output[i]<<1; k--; } k=7; }}
int EP(unsigned char *EPplaintext,unsigned char *plaintext){ unsigned char EPmap[]={ 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 }; int i; int j; int k=7; for(i=0;i<6;i++){ for(j=0;j<8;j++){ EPplaintext[i]=EPplaintext[i]+getbit(EPmap[j+i*8]%8,plaintext[(EPmap[j+i*8]-1)/8]); if(k>0) EPplaintext[i]=EPplaintext[i]<<1; k--; } k=7; } return 1;}
int F(unsigned char *r,unsigned char *k,unsigned char *output){ unsigned char s1[4][16]={ {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} }; unsigned char s2[4][16]={ {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} }; unsigned char s3[4][16]={ {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} }; unsigned char s4[4][16]={ {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} }; unsigned char s5[4][16]={ {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} }; unsigned char s6[4][16]={ {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} }; unsigned char s7[4][16]={ {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} }; unsigned char s8[4][16]={ {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 temp[6]; unsigned char temp1[8]={0}; int i; unsigned char x[8]={0}; unsigned char y[8]={0}; unsigned char EPplaintext[6]; unsigned char output1[4]={0};
EP(EPplaintext,r); for(i=0;i<6;i++) temp[i]^=k[i];
temp1[0]=(temp[0]>>2);
temp1[1]=(temp[0]&3); temp1[1]<<=2; temp1[1]=temp1[1]+(temp[1]>>4);
temp1[2]=(temp[1]&15); temp1[2]<<=4; temp1[2]=temp1[2]+(temp[2]>>6);
temp1[3]=(temp[2]&63);
temp1[4]=(temp[3]>>2);
temp1[5]=(temp[3]&3); temp1[5]<<=2; temp1[5]=temp1[5]+(temp[4]>>4);
temp1[6]=(temp[4]&15); temp1[6]<<=4; temp1[6]=temp1[6]+(temp[5]>>6);
temp1[7]=(temp[5]&63);
for(i=0;i<8;i++){ x[i]+=getbit(3,temp1[i]); x[i]<<=1; x[i]+=getbit(8,temp1[i]); y[i]+=getbit(4,temp1[i]); y[i]<<=1; y[i]+=getbit(5,temp1[i]); y[i]<<=1; y[i]+=getbit(6,temp1[i]); y[i]<<=1; y[i]+=getbit(7,temp1[i]); }
output1[0]+=s1[x[0]][y[0]]; output1[0]<<=4; output1[0]+=s2[x[1]][y[1]];
output1[1]+=s3[x[2]][y[2]]; output1[1]<<=4; output1[1]+=s4[x[3]][y[3]];
output1[2]+=s5[x[4]][y[4]]; output1[2]<<=4; output1[2]+=s6[x[5]][y[5]];
output1[3]+=s7[x[6]][y[6]]; output1[3]<<=4; output1[3]+=s8[x[7]][y[7]];
P(output,output1); return 1;}
void P(unsigned char *output,unsigned char *input){ unsigned char map1[]={ 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 }; int i; int j; int k=7;
for(i=0;i<4;i++){ for(j=0;j<8;j++){ output[i]=output[i]+getbit(map1[j+i*8]%8,input[(map1[j+i*8]-1)/8]); if(k>0) output[i]=output[i]<<1; k--; } k=7; }}
void FK(unsigned char *l,unsigned char *r,unsigned char *sk,unsigned char *output){ int i; unsigned char result[4]={0}; F(r,sk,result); for(i=0;i<4;i++) result[i]^=l[i]; for(i=0;i<4;i++) output[i]=r[i]; for(i=4;i<8;i++) output[i]=result[i-4];}
int PC1(unsigned char *cd,unsigned char *input){ unsigned char map1[]={ 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 }; int i; int j; int k=7; for(i=0;i<7;i++){ for(j=0;j<8;j++){ cd[i]=cd[i]+getbit(map1[j+i*8]%8,input[(map1[j+i*8]-1)/8]); if(k>0) cd[i]=cd[i]<<1; k--; } k=7; } return 1;}
int PC2(unsigned char *output,unsigned char *input){ unsigned char map1[]={ 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 }; int i; int j; int k=7; for(i=0;i<6;i++){ for(j=0;j<8;j++){ output[i]=output[i]+getbit(map1[j+i*8]%8,input[(map1[j+i*8]-1)/8]); if(k>0) output[i]=output[i]<<1; k--; } k=7; } return 1;}
int LS1(unsigned char *input){ int i[4]={0}; int j[4]={0}; unsigned char temp=0; unsigned char temp1=0; if(getbit(1,input[0])==1)i[0]=1; if(getbit(1,input[1])==1)i[1]=1; if(getbit(1,input[2])==1)i[2]=1; if(getbit(1,input[3])==1)i[3]=1; input[0]<<=1; input[1]<<=1; input[2]<<=1; input[0]+=i[1]; input[1]+=i[2]; input[2]+=i[3];
if(getbit(5,input[3])==1)j[0]=1; if(getbit(1,input[4])==1)j[1]=1; if(getbit(1,input[5])==1)j[2]=1; if(getbit(1,input[6])==1)j[3]=1; input[4]<<=1; input[5]<<=1; input[6]<<=1; input[4]+=j[2]; input[5]+=j[3]; input[6]+=j[0];
temp=input[3]; temp1=input[3]; temp<<=1; temp>>=5; temp<<=1; if(i[0]==1) temp+=1; temp<<=4;
temp1<<=1; if(j[1]==1) temp1=temp1+1; temp1&=15;
input[3]=temp+temp1; return 1;}
int is_InputKeyRight(char *inputkey)//输入的密钥只能为8位的字符串{ if(strlen(inputkey)!=8) return 0; return 1;}
void GenerateSubkey(char sk[16][6],char *inputkey){ int i; unsigned char destkey[7]={0}; unsigned char lstime[]={ 1,1,2,2,2,2,2,2, 1,2,2,2,2,2,2,1 };
PC1(destkey,inputkey); for(i=0;i<16;i++){ LS1(destkey); if(lstime[i]==2) LS1(destkey); PC2(sk[i],destkey); }}
void des(unsigned char *output,unsigned char *plaintext,unsigned char sk[16][6],int flag)//flag==0crypt;flag==1decrypt{ unsigned char step1[8]={0}; unsigned char step2[8]={0}; unsigned char stepr[4]={0}; unsigned char stepl[4]={0}; unsigned char temp[4]; int i; int j; IP(step1,plaintext); for(i=0;i<4;i++) stepl[i]=step1[i]; for(i=0;i<4;i++) stepr[i]=step1[i+4]; if (flag==0){ for(j=0;j<16;j++){ FK(stepl,stepr,sk[j],step2); for(i=0;i<4;i++) stepl[i]=step2[i]; for(i=0;i<4;i++) stepr[i]=step2[i+4]; } } else{ for(j=0;j<16;j++){ FK(stepl,stepr,sk[15-j],step2); for(i=0;i<4;i++) stepl[i]=step2[i]; for(i=0;i<4;i++) stepr[i]=step2[i+4]; } } for(i=0;i<4;i++) temp[i]=step2[i]; for(i=0;i<4;i++) step2[i]=step2[i+4]; for(i=0;i<4;i++) step2[i+4]=temp[i]; IP1(output,step2);}
void arrayxor(unsigned char *dest,unsigned char *input){ int i; for(i=0;i<8;i++) dest[i]=input[i]^dest[i];}
int Crypt(char *sourcepath,char *destpath,char *inputkey,char *inputiv){ unsigned char plaintext[8]={0}; unsigned char sk[16][6]={0}; unsigned char output[8]={0}; unsigned char temp[8]={0}; int i; int j; int filesize; int crypttimes; FILE *fsource; FILE *fdest;
for(i=0;i<8;i++) temp[i]=inputiv[i]; GenerateSubkey(sk,inputkey); fsource=fopen(sourcepath,"rb"); fdest=fopen(destpath,"wb"); fseek(fsource,0,2); filesize=ftell(fsource); rewind(fsource); crypttimes=filesize/8;
while(crypttimes>0){ fread(plaintext,8,1,fsource); arrayxor(plaintext,temp); des(output,plaintext,sk,0); fwrite(output,8,1,fdest); crypttimes--; for(i=0;i<8;i++){ temp[i]=output[i]; output[i]=0; } }
if(filesize%8!=0){ fread(plaintext,filesize%8,1,fsource); for(i=0;i<8-(filesize%8);i++){ plaintext[filesize%8+i]=255; } arrayxor(plaintext,temp); des(output,plaintext,sk,0); fwrite(output,8,1,fdest); } i=filesize%8; fputc(i,fdest); fclose(fsource); fclose(fdest);
return 1;}
int Decrypt(char *sourcepath,char *destpath,char *inputkey,char *inputiv){ unsigned char plaintext[8]={0}; unsigned char sk[16][6]={0}; unsigned char output[8]={0}; unsigned char temp[8]={0}; int i; int filesize; int crypttimes; FILE *fsource; FILE *fdest; int flag;
for(i=0;i<8;i++) temp[i]=inputiv[i]; GenerateSubkey(sk,inputkey); fsource=fopen(sourcepath,"rb"); fdest=fopen(destpath,"wb"); fseek(fsource,0,2); filesize=ftell(fsource); rewind(fsource); crypttimes=filesize/8; fseek(fsource,filesize-1,0); flag=fgetc(fsource); rewind(fsource);
while(crypttimes>1){ fread(plaintext,8,1,fsource); des(output,plaintext,sk,1); arrayxor(output,temp); fwrite(output,8,1,fdest); crypttimes--; for(i=0;i<8;i++){ temp[i]=plaintext[i]; output[i]=0; } }
if(flag!=0){ fread(plaintext,8,1,fsource); des(output,plaintext,sk,1); arrayxor(output,temp); fwrite(output,flag,1,fdest); } fclose(fsource); fclose(fdest); return 1;}
int Check(int argc,char **argv){ if(argc!=6){ printf("命令长度有错误。\n"); return 0; } if(is_Sourcepathright(argv[1])==0){ return 0; } if(is_Destpathright(argv[2])==0){ return 0; } if(is_InputKeyRight(argv[3])==0){ printf("输入的密钥不正确。\n"); return 0; } if(is_InputKeyRight(argv[4])==0){ printf("输入的矢量不正确。\n"); return 0; } if(strlen(argv[5])>1){ printf("错误的加解密类型。\n"); return 0; } if(argv[5][0]!='e'&&argv[5][0]!='E'&&argv[5][0]!='d'&&argv[5][0]!='D'){ printf("错误的加解密类型。\n"); return 0; } return 1;}
int is_Sourcepathright(char *source_path){ FILE *fp; if ((fp=fopen(source_path,"rb"))==NULL){ printf("您所输入的文件不存在."); fclose(fp); return 0; } else{ fclose(fp); return 1; }}
int is_Destpathright(char *dest_path){ FILE *fp; if ((fp=fopen(dest_path,"wb"))==NULL){ printf("输入的路径不正确."); fclose(fp); return 0; } else{ fclose(fp); return 1; }}
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