凯撒密码，C语言，求救！(凯撒密码加密解密C语言)
凯撒密码，C语言，求救！(凯撒密码加密解密C语言)
#include stdio.h
#include string.h
int main()
{
int i = 0;
int len = 0;
char ch;
char buf[256] = {0};
char nor[26] = {'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
char enc[26] = {'s','u','w','y','a','c','e','g','i','k','m','o','q','r','t','v','x','z','b','d','f','h','j','l','n','p'};
printf("Encode or Decode: ");
scanf("%c",ch);
printf("please input your string: ");
fflush(stdin);
gets(buf);
len = strlen(buf);
switch (ch)
{
case 'e':
case 'E':
for (i=0;ilen;i++)
{
buf[i] = enc[buf[i] - 'a'];
}
break;
case 'd':
case 'D':
for (i=0;ilen;i++)
{
buf[i] = nor[i];
}
break;
default:
printf("wrong input!\n");
}
printf("%s\n",buf);
return 0;
}
凯撒密码就是简单的加上一个数，'a'+3='d';'z'+3='c' 假设原文全是小写字母，那么 char plain[N]={...}; //明文 char cipher[N]={};//密文 int key=3; int i=0,temp; for(i=0;iN;i++) {if(plain[i]!=' ') {temp=plain[i]+key-'a'; temp=temp%26; cipher[i]=temp+'a'; } else cipher[i]=plain[i]; } 这样就完成了加密，密文数组里面就是对原文加密后的密文，key是密钥。
#includestdio.h
#includeconio.h char encrypt(char ch,int n)/*加密函数，把字符向右循环移位n*/
{
while(ch=Ach=Z)
{
return (A+(ch-A+n)%26);
}
while(ch=ach=z)
{
return (a+(ch-a+n)%26);
}
return ch;
}void menu()/*菜单，1.加密，2.解密，3.暴力破解，密码只能是数字*/
{
clrscr();
printf("\n===============================================================================");
printf("\n1.Encrypt the file");
printf("\n2.Decrypt the file");
printf("\n3.Force decrypt file");
printf("\n4.Quit\n");
printf("===============================================================================\n");
printf("Please select a item:");
return;
}void logo()/*显示版权信息*/
{
printf("\nZhensoft Encryption [Version:1.0.0]");
printf("\nCopyright (C) 2004 Zhensoft Corp.\n");
printf("\n \n");
return;
}
main()
{
int i,n;
char ch0,ch1;
FILE *in,*out;
char infile[20],outfile[20];textbackground(BLACK);
textcolor(LIGHTGREEN);
clrscr();logo();
sleep(3);/*等待3秒*/menu();
ch0=getch();while(ch0!=4)
{
if(ch0==1)
{
clrscr();
printf("\nPlease input the infile:");
scanf("%s",infile);/*输入需要加密的文件名*/ if((in=fopen(infile,"r"))==NULL)
{
printf("Can not open the infile!\n");
printf("Press any key to exit!\n");
getch();
exit(0);
} printf("Please input the key:");
scanf("%d",n);/*输入加密密码*/ printf("Please input the outfile:");
scanf("%s",outfile);/*输入加密后文件的文件名*/ if((out=fopen(outfile,"w"))==NULL)
{
printf("Can not open the outfile!\n");
printf("Press any key to exit!\n");
fclose(in);
getch();
exit(0);
} while(!feof(in))/*加密*/
{
fputc(encrypt(fgetc(in),n),out);
} printf("\nEncrypt is over!\n");
fclose(in);
fclose(out);
sleep(1);
} if(ch0==2)
{
clrscr();
printf("\nPlease input the infile:");
scanf("%s",infile);/*输入需要解密的文件名*/ if((in=fopen(infile,"r"))==NULL)
{
printf("Can not open the infile!\n");
printf("Press any key to exit!\n");
getch();
exit(0);
} printf("Please input the key:");
scanf("%d",n);/*输入解密密码（可以为加密时候的密码）*/ n=26-n; printf("Please input the outfile:");
scanf("%s",outfile);/*输入解密后文件的文件名*/ if((out=fopen(outfile,"w"))==NULL)
{
printf("Can not open the outfile!\n");
printf("Press any key to exit!\n");
fclose(in);
getch();
exit(0);
} while(!feof(in))
{
fputc(encrypt(fgetc(in),n),out);
}
printf("\nDecrypt is over!\n");
fclose(in);
fclose(out);
sleep(1);
} if(ch0==3)
{
clrscr();
printf("\nPlease input the infile:");
scanf("%s",infile);/*输入需要解密的文件名*/ if((in=fopen(infile,"r"))==NULL)
{
printf("Can not open the infile!\n");
printf("Press any key to exit!\n");
getch();
exit(0);
} printf("Please input the outfile:");
scanf("%s",outfile);/*输入解密后文件的文件名*/ if((out=fopen(outfile,"w"))==NULL)
{
printf("Can not open the outfile!\n");
printf("Press any key to exit!\n");
fclose(in);
getch();
exit(0);
} for(i=1;i=25;i++)/*暴力破解过程，在察看信息正确后，可以按Q或者q退出*/
{
rewind(in);
rewind(out);
clrscr();
printf("===============================================================================\n");
printf("The outfile is:\n");
printf("===============================================================================\n");
while(!feof(in))
{
ch1=encrypt(fgetc(in),26-i);
putch(ch1);
fputc(ch1,out);
}
printf("\n===============================================================================\n");
printf("The current key is: %d \n",i);/*显示当前破解所用密码*/
printf("Press Q to quit and other key to continue......\n");
printf("===============================================================================\n");
ch1=getch();
if(ch1==q||ch1==Q)/*按Q或者q时退出*/
{
clrscr();
logo();
printf("\nGood Bye!\n");
fclose(in);
fclose(out);
sleep(3);
exit(0);
}
} printf("\nForce decrypt is over!\n");
fclose(in);
fclose(out);
sleep(1);
}
menu();
ch0=getch();
}
clrscr();
logo();
printf("\nGood Bye!\n");
sleep(3);
}
