凯撒密码加解密程序（C语言） 2009年09月30日 星期三 13:21 1、程序结构化，用函数分别实现 2、对文件的加密，解密输出到文件
#include #include
void menu()/菜单，1.加密 2.解密 3.退出/ { clrscr(); printf(" ==============================================================================="); printf(" 1.Encrypt the file"); printf(" 2.Decrypt the file"); printf(" 3.Quit "); printf("=============================================================================== "); printf("Please select a item:"); return; }
char encrypt(char ch,int n)/加密函数，把字符向右循环移位n/ { while(ch>=‘A’&&ch=‘a’&&ch<=‘z’) { return (‘a’+(ch-‘a’+n)%26); } return ch; }
main() { int i,n; char ch0,ch1; FILE *in,*out; char infile[10],outfile[10];
textbackground(RED); textcolor(LIGHTGREEN); clrscr();
menu(); ch0=getch();
while(ch0!=‘3’) { if(ch0==‘1’) { clrscr(); printf(" Please 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! 讯享网
");
讯享网printf("Press any key to exit!
");
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) {
讯享网printf("Can not open the outfile!
");
printf("Press any key to exit! ");
讯享网fclose(in); getch(); exit(0);
}
while(!feof(in))/加密/ {
fputc(encrypt(fgetc(in),n),out); }
printf(" Encrypt is over! "); fclose(in); fclose(out); sleep(1); }
if(ch0==‘2’) { clrscr();
讯享网 printf("
Please input the infile:"); scanf("%s",infile);/输入需要解密的文件名/
if((in=fopen(infile,"r"))==NULL) {
讯享网printf("Can not open the infile!
");
printf("Press any key to exit! ");
讯享网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! ");
讯享网printf("Press any key to exit!
");
fclose(in); getch(); exit(0); }
while(!feof(in)) {
讯享网fputc(encrypt(fgetc(in),n),out);
} printf(" Decrypt is over! "); fclose(in); fclose(out); sleep(1); }
clrscr();
printf(" Good Bye! "); sleep(3);
讯享网getch();
} }
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