标题：【Code§C/C++】密码程序  
出处：Felix021
时间：Tue, 28 Aug 2007 22:16:16 +0000
作者：felix021
地址：https://www.felix021.com/blog/read.php?275

内容：
【Code§C/C++】密码程序  
 这个程序可以修改密码，依靠一个文件来保存的 
密码有经过简单的加密 


#include <stdio.h> 
#include <stdlib.h> 
#include <string.h> 

int menu(); 
int verify(int choice); 
int change(); 
int reboot(); 
int write(char *pass); 
int read(char *pass); 

FILE *fp=NULL; 

int main() 
{ 
  int choice=0,a,b,c; 
  while(choice<1||choice>3)choice=menu(); 
  switch(choice) 
  { 
    case 1: 
      a=verify(1); 
      if(a) 
      {  
        printf("Right password^_^\n"); 
        return 0; 
      } 
      else reboot(); 
      break; 
    case 2: 
      a=verify(2); 
      if(a)change(); 
      else reboot(); 
      break; 
    case 3: 
      reboot(); 
      break; 
    default: 
      reboot(); 
  } 
  return 0; 
} 

int menu() 
{ 
  char input[200]; 
  int i; 
  printf("\n\nWhat do you want to do?\n"); 
  printf("\t1. Enter password and use MSDOS\n"); 
  printf("\t2. Change password\n"); 
  printf("\t3. I don't know the password, reboot\n"); 
  printf("Input your choice: "); 
  fflush(stdin); 
  gets(input); 
  fflush(stdin); 
  for(i=0;input[i];i++) 
    if(input[i]<='9'&input[i]>='1')break;   
  switch(input[i]) 
  { 
    case '1':return 1; 
    case '2':return 2; 
    case '3':return 3; 
    default :return 0;   
  } 
} 

int verify(int choice) 
{ 
  if((fp=fopen("pass.dat","rb+"))==NULL)  
  { /*无密码文件，创建*/  
    printf("Currently there's no password.\n"); 
    if((fp=fopen("pass.dat","w"))==NULL) 
    { /*无法创建*/ 
      printf("Unable to create a file."); 
      return 0; 
    } 
    else 
    { /*建立好了文件，修改密码*/ 
      fclose(fp); 
      if(choice==2)return 1; 
      return change(); 
    }  
  } 
  else /*密码文件存在*/  
  { 
    int times=0; 
    char pass[20]; 
    char temp[20]; 
    read(temp); 
    while(times<3) 
    { 
      printf("Please input the password: "); 
      gets(pass); 
      fflush(stdin); 
      if(strcmp(pass,temp)==0)return 1; 
      else printf("Bad password.\n"); 
      times++; 
    } 
    printf("\nYou have wrongly inputted the password 3 times."); 
    return 0; 
  } 
} 

int change() 
{ 
  char pass1[20]; 
  char pass2[20]; 
  if((fp=fopen("pass.dat","w"))==NULL) 
  { /*无法创建*/ 
    printf("Unable to create a file."); 
    return 0; 
  } 
  else 
  { 
    changepass: 
    printf("Please enter  new  password: "); 
    gets(pass1); 
    if(pass1[0]==0) goto changepass; 
    fflush(stdin); 
    printf("Please confirm the password: "); 
    gets(pass2); 
    fflush(stdin); 
    if(strcmp(pass1,pass2)==0) 
    { 
      write(pass1); 
      return 1; 
    } 
    else 
    { 
      printf("Two passwords don't match!\n"); 
      goto changepass; 
    } 
  } 
} 

int reboot() 
{ 
  printf("\nThis computer will reboot now.\n"); 
  system("pause"); 
  system("off r"); 
} 

int read(char *pass) 
{ 
  int i=0; 
  fread(pass,sizeof(char),20,fp); 
  fclose(fp); 
  for(i=0;i<20;i++) 
    pass[i]-=i; 
  return 0; 
}  

int write(char *pass) 
{ 
  int i=0; 
  for(i=0;i<20;i++) 
    pass[i]+=i; 
  fwrite(pass,sizeof(char),20,fp); 
  fclose(fp); 
  return 0; 
}  

 



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