/*
 crypt.c
 written by Ben Fasenfest
 on: 11/22/96
 Encrypts / decrypts files with a password
*/
 
#include <stdlib.h>
#include <stdio.h>
#include "ansi.c"
 
char menu();        /* displays main menu and returns choic */
 
int take_action(char choice); /* I changed take_action to return a value so
                                   that the program can exit from the main()
                                   function or loop back to the main menu
                                   I assumed that this had to be or else there
                                   would not be a quit function on the menu */
 
unsigned int code(void);      /*prompts for password and returns code value */
 
unsigned char crypt(unsigned char in, char mode, unsigned char codefactor);
          /*the actual encryption function */
 
void aprint(char *what, int attrib);    /* takes a character string and prints
                                             it to the screen with an attribute */
 
void header(void);            /* prints the header to the top of each screen */
 
FILE *file=NULL, *ofile=NULL;
 
int main(void)
{
char choice;
int ret;
 
do {
     choice=menu();
     fcloseall();
     }
while((ret=take_action(choice)) !=0);
if(isansi()==1)
     ansi_clrscrn();
printf("Thankyou for using\nNSCRYPT File encrypter / decrypter\n\tCopyright 1996 by NebSoft Inc.\n\tWritten by Ben Fasenfest.\n");
return ret;
}
 
char menu()
{
char rc;
 
header();
printf("\t\t------------MAIN MENU------------");
printf("\n\n\t\t\ta) encrypt a file\n\t\t\tb) decrypt a file\n\t\t\tc) quit");
printf("\n\n\t\tPlease enter your choice --> ");
do
     {
     rc=getche();
     if(rc!='a' && rc!='b' && rc!='c')
          printf("\n\n\t\tThat is not a choice.\n\t\tPlease enter your choice --> ");
     }
while(rc!='a' && rc!='b' && rc!='c');
return rc;
}
 
int take_action(char choice)
{
char iname[50];
char oname[50];
unsigned char ch;
int c, ret=1;
unsigned int cd;
 
if(choice=='a')
     {
     header();
     printf("What is the name of the file to encrypt ? ");
     fflush(stdin);
     scanf("%s", iname);
     if((file=fopen(iname,"r")) !=NULL)
          {
          cd=code();
          printf("\n\nDo you want the encrypted file\n\n\ta) saved to another file\n\tb) printed on the screen");
          do {
              printf("\n\nEnter your choice --> ");
              ch=getche();
              if(ch!='a' && ch!='b')
              printf("\nThat is not a choice.");
              }
          while(ch!='a' && ch!='b');
          if(ch=='a')
               {
               printf("\n\nPlease enter the name of the file to save to --> ");
               fflush(stdin);
               scanf("%s",oname);
               if((ofile=fopen(oname,"w"))!=NULL)
                    {
                    while((c=getc(file)) !=EOF)
                         {
                         fprintf(ofile, "%c", crypt(c, 'e', cd));
                         }
                    printf("\n\nFile %s encrypted and saved as %s\n",iname,oname);
                    }
               else {
                    printf("\n\nThe file %s cannot be written to.\n", oname);
                    }
               }
          else {
               printf("\n");
               while((c=getc(file)) !=EOF)
                    {
                    ch=crypt(c,'e',cd);
                    if(ch!=7)                /* 7 is the bell - really annoying */
                         printf("%c", ch);
                    }
               printf("\n\n");
               }
          }
     else
          printf("\n\nThe file %s cannot be found.\n", iname);
     }
else if(choice=='b')
     {
     header();
     printf("What is the name of the file to decrypt ? ");
     fflush(stdin);
     scanf("%s", iname);
     if((file=fopen(iname,"r")) !=NULL)
          {
          cd=code();
          printf("\n\nDo you want the decrypted file\n\n\ta) saved to another file\n\tb) printed on the screen");
          do {
               printf("\n\nEnter your choice --> ");
               ch=getche();
               if(ch!='a' && ch!='b')
                    printf("\nThat is not a choice.");
               }
          while(ch!='a' && ch!='b');
          if(ch=='a')
               {
               printf("\n\nPlease enter the name of the file to save to --> ");
               fflush(stdin);
               scanf("%s",oname);
               if((ofile=fopen(oname,"w"))!=NULL)
                    {
                    while((c=getc(file)) !=EOF);
                         fprintf(ofile, "%c", crypt(c, 'd', cd));
                    printf("File %s decrypted and saved as %s\n",iname,oname);
                    }
                else printf("\n\nThe file %s cannot be written to.\n", oname);
               }
          else {
               printf("\n");
               while((c=getc(file)) !=EOF)
                    {
                    ch=crypt(c,'d',cd);
                    if(ch!=7)                /* 7 is the bell - really annoying */
                         printf("%c", ch);
                    }
               printf("\n\n");
               }
          }
     else printf("\n\nThe file %s cannot be found.\n", iname);
     }
else if(choice=='c')
          ret= 0;
if(ret==1)
     {
     printf("(Press any key to continue)");
     getch();
     }
return ret;
}
 
unsigned int code(void)
{
char password[4];
char * pntr;
unsigned int pnumber;
int c;
 
do
     {
     printf("\nPlease enter the password (three letters, lower case) -->");
     for(c=0;c<3;c++)
          {
          password[c]=getch();
          printf("*");
          }
     if( password[0] < 97 ||  password[0] > 122 ||  password[1] < 97
          ||  password[1] > 122 ||  password[2] < 97 ||  password[2] > 122)
              printf("\n\nThat password is not all lower case letters.");
     }
while( password[0] < 97 ||  password[0] > 122 ||  password[1] < 97
     ||  password[1] > 122 ||  password[2] < 97 ||  password[2] > 122);
 
pntr=password;                 /* my formula is not bombproof - there some different passwords that will return the same value */
pnumber= (*pntr-96);
pntr++;
pnumber+= 2* (*pntr-96);
pntr++;
pnumber+= 3* (*pntr-96);
pnumber+=2;
return pnumber;
}
 
unsigned char crypt(unsigned char in, char mode, unsigned char codefactor)
{
int ch;
 
if(mode=='e')
     {
     ch=in-codefactor;
     if(ch < 1)
          ch=ch+255;
     if( ch==26)          /* eof character-don't want to put it to file */
          ch=0;
     }
else
     {
     if(ch==0)           /* converts 0 back to eof */
          ch=26;
     ch=in+codefactor;
     if(ch>255)
          ch=ch-255;
     }
 
return ch;
}
 
 
void aprint(char *what, int attr)
{
char *pntr;
int row, col;
pntr=what;
 
 
row=cursrow();
col=curscol();
while(*pntr!=0)
     {
     writechs(*pntr,attr,1);
     pntr++;
     poscurs(row, ++col);
     }
}
 
void header(void)
{
int attr1;
int attr2;
int fg,bg;
 
if(MONOCHROME)    /*detect card type */
     {                             /* monochrome */
     attr1=0x07;
     attr2=0x09;
     }
else {                             /* color */
     attr1= 0x17;
     attr2= 0x1F;
     fg=ANSI_FG_WHITE;
     bg=ANSI_BG_BLUE;
     }
if(isansi()==0)
     clrscrn2(attr1);
else ansi_clrscrn2(fg, bg);
printf("\n\t\t");
aprint("NSCRYPT File encrypter / decrypter",attr2);
printf("\n\t\t");
aprint("Copyright 1996 by NebSoft Inc.", attr2);
printf("\n\t\t");
aprint("Written by Ben Fasenfest.", attr2);
printf("\n\n");
}