用c语言设计一个文件加密的程序,并以此写一篇文件加密程序论文!急~~

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#define N 5
void main(){
FILE *fp;
int i=1;
char ch;
char password1[30]="admin";//输入密码为admin，绝对加密
char password2[30];

if((fp=fopen("c:\\file.txt","a+"))==NULL){
printf("Cannot open file.\n");
exit(0);
}
printf("请输入一些信息\n");
fputs("\n",fp);
ch=getchar();
while(ch!='\n'){
fputc(ch,fp);
ch=getchar();
}
fputs("\n",fp);

rewind(fp);
ch=fgetc(fp);
while(ch!=EOF){
printf("%c",ch+5);
ch=fgetc(fp);
}
printf("\n\n*********************\n\n");
printf("请输入密码，有%d次机会:\n",N);
gets(password2);
while(strcmp(password1,password2)!=0&&i<