/*
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和樓上的相比,或許 看上去很煩
ch[i] +=5;
if (ch[i] 'Z')
{
ch[i] -= 26;
}
可以改成和 樓上的 方法
等價(jià)于 ch[i] = 'A' + (ch[i] - 'A' + 5) % 26;
*/
# include stdio.h
# include stdlib.h //用到了system(); 不寫 ,可以用 getchar();
#define strwidth 117 //定義長(zhǎng)度
int main(void)
{
char ch[strwidth];
int i ;
printf("請(qǐng)輸入密碼:");
gets(ch); //輸入數(shù)據(jù),用gets(); 保留了空格
for (i = 0; i strwidth ;i++ )
{
if (ch[i] = 'a' ch[i] = 'z' ) //判斷是否小寫字母
{
ch[i] +=5;
if (ch[i] 'z') //不解釋,我想這樣,理解可能會(huì)方便點(diǎn)吧
{
ch[i] -= 26;
}
}
else if ( ch[i] = 'A' ch[i] = 'Z') //判斷是否大寫字母
{
ch[i] +=5;
if (ch[i] 'Z')
{
ch[i] -= 26;
}
}
}
printf("加密后為:%s\n" , ch); //輸出數(shù)據(jù)
system("pause");
return 0;
}
/*
或者 這樣
*/
# include stdio.h
# include stdlib.h //用到了system(); 不寫 ,可以用 getchar();
#define strwidth 117 //定義長(zhǎng)度
int main(void)
{
char ch[strwidth];
int i ;
printf("請(qǐng)輸入密碼:");
gets(ch); //輸入數(shù)據(jù),用gets(); 保留了空格
for (i = 0; i strwidth ;i++ )
{
if (ch[i] = 'a' ch[i] = 'z' || ch[i] = 'A' ch[i] = 'Z' ) //判斷是否是字母
{
ch[i] +=5;
if ( ch[i]'Z' ch[i] = 'Z' + 5 || ch[i] 'z' )
{
ch[i] -= 26;
}
}
}
printf("加密后為:%s\n" , ch); //輸出數(shù)據(jù)
system("pause");
return 0;
}
凱撒密碼是一種非常古老的加密方法，相傳當(dāng)年凱撒大地行軍打仗時(shí)為了保證自己的命令不被敵軍知道，就使用這種特殊的方法進(jìn)行通信，以確保信息傳遞的安全。他的原理很簡(jiǎn)單，說到底就是字母于字母之間的替換。下面讓我們看一個(gè)簡(jiǎn)單的例子：“baidu”用凱撒密碼法加密后字符串變?yōu)椤癳dlgx”，它的原理是什么呢？把“baidu”中的每一個(gè)字母按字母表順序向后移3位，所得的結(jié)果就是剛才我們所看到的密文。
#include stdio.h
main()
{
char M[100];
char C[100];
int K=3,i;
printf("請(qǐng)輸入明文M(注意不要輸入空白串)\n");
gets(M);
for(i=0;M[i]!='\0';i++)
C[i]=(M[i]-'a'+K)%26+'a';
C[i]='\0';
printf("結(jié)果是:\n%s\n",C);
}
#includestdio.h
#includeconio.h char encrypt(char ch,int n)/*加密函數(shù)，把字符向右循環(huán)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()/*菜單，1.加密，2.解密，3.暴力破解，密碼只能是數(shù)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()/*顯示版權(quán)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);/*輸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);/*輸入加密密碼*/ printf("Please input the outfile:");
scanf("%s",outfile);/*輸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);/*輸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);/*輸入解密密碼（可以為加密時(shí)候的密碼）*/ n=26-n; printf("Please input the outfile:");
scanf("%s",outfile);/*輸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);/*輸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);/*輸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++)/*暴力破解過程，在察看信息正確后，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);/*顯示當(dāng)前破解所用密碼*/
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時(shí)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);
}
重慶分公司
重慶分公司
