C > Beginners Lab Assignments

encryption and decryption of files

encryption and decryption of files

ď»żIn  main function we declare required variable.

printf(" enter choice

	 1)encode
	 2)view ecoded file
	 3)
decode
	            4)view decoced file
	 5)exit			 ------");
// this is to print the main menu
scanf("%d",&ch);                                             // entering
of choice
while(ch!=5)                                                    //  until
choice is exit
{
  if(ch==1)                                                        //if
choice is to encrypt
   {
     scanf("%s",name);                                      // accept file
name
     scanf("%c",&ff);                                         //accept the
choice of change

// the file position or not
     if(ff=='c'||ff=='C')
   {strcpy(encri,ruf);scanf("%s",encri);} // so as to change enter file path

     cscanf("%s",pass);                                     // enter
password
     l=strlen(pass);                                            // l
=string length of password

    st=fopen(name,"r");                                   //  open the
file to be encrypted
     ed=fopen(encri,"w");                                // open the file
to where to be
                                                                       //
encrypted
     while(!feof(st))                                        // until end
of file to be encrypted
     {  x=fgetc(st);                                         // read each
character into X
        fputc(x+pass[i++%l],ed);                    // write the sum of X
and password
    }                                                               //
char
     fclose(st);                                        // close first
file
     fclose(ed);                                      // close second file
}
if(ch==3)                                             // if choice is
decryption
   {
      scanf(â€ś%sâ€ť,encri);                        //enter the file name
to be decrypted
      ed=fopen(encri,"r");                     //open  the above mentioned
file
      scanf("%c",&ff);                          //accept the choice of
change
                                                           // the file
position or not

      if(ff=='c'||ff=='C')
    { strcpy(decri,ruf);
      scanf("%s",decri);                // so as to change enter file path
     }
      cscanf("%s",pass);                      // enter password
      de=fopen(decri,"w");                  //open a file to store decoded
data
      while(!feof(ed))                          // until end of file to be
encrypted
      {
         x=fgetc(ed);                             // read each character
into X
   fputc(x-pass[i++%l],de);        // write the sum of X and password
    }                                                   // char


      fclose(ed);                                 // close first file
      fclose(de);                                // close second file
      }

 if(ch==2)                                 //if choice is to view the
contents encoded file
  {
    ed=fopen(encri,"r");             //open that file and read each
character
    while(!feof(ed))
    printf("%c",fgetc(ed));          //print them until end of file
    fclose(ed);                             // close this file
  }
 if(ch==4)                                 //if choice is to view the
contents decoded file
 {
  ed=fopen(decri,"r");               //open that file and read each
character
  while(!feof(ed))
  printf("%c",fgetc(ed)) ;          //print them until end of file
  fclose(ed) ;                              // close this file
  }

   scanf("%d",&ch);                  // enter the choice from menu
  }                                              // end while
}                                                 // end main