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


unsigned long a,b[128],index2;
unsigned int r,cle;

/* CARACACHS Cipher (c) Alexandre PUKALL 2000 */
/* 256 bits CIPHER */
/* Code free for all, even for commercial application */
/* Public domain */

int stream(unsigned int *r,unsigned long *index2,unsigned long *a,unsigned long *b)
{
  b[*index2] = ( b[*index2] * (*a) ) + 1;
  *r = (*r + (( b[*index2] >> 16 ) & 0x7fff));
  *r = (*r << (*r%16)) | (*r >> (16-(*r%16)));
  return(0);
}

unsigned char pc3encode(unsigned char byte)
{
  unsigned short d;

     for (index2=0;index2<=(cle-1);index2++)
     {
       stream(&r,&index2,&a,b);
     }
   d=byte;
   byte=byte^(r&255);
   r=r+d;
   b[cle-1]=b[cle-1]+d;
   return(byte);
}

unsigned char pc3decode(unsigned char byte)
{
  unsigned short d;

     for (index2=0;index2<=(cle-1);index2++)
     {
       stream(&r,&index2,&a,b);
     }
   byte=byte^(r&255);
   d=byte;
   r=r+d;
   b[cle-1]=b[cle-1]+d;
   return(byte);
}


int pc3init(unsigned int lngkey,unsigned char key[258])
{
   unsigned int z,y,x,i,reste;
   unsigned char tab[258],plain;
   if (lngkey>256) lngkey=256;
   if (lngkey<1)
   {
     lngkey=1;
     strcpy(key,"a");
   }

   x=lngkey;

   for (i=0;i<x;i++)
   {
     tab[i]=key[i];
   }

   reste=lngkey%2;
   cle=lngkey/2;
   if (reste!=0) cle=cle+1;

   for (z=0;z<128;z++)
   {
    b[z]=0;
   }

   y=0;
   for (z=0;z<=(cle-1);z++)
   {
    if ( (z==(cle-1))&&(reste!=0) )
     {
       b[z]=(key[y]*256)%65536;
     }
    else
     {
       b[z]=((key[y]*256)%65536)+key[y+1];
       y=y+1;
     }
    y=y+1;
   }

   r=0;
   a=0x015a4e35;

     for (index2=0;index2<=(cle-1);index2++)
     {
       for(z=0;z<=index2;z++)
       {
       stream(&r,&index2,&a,b);
       }
     }

   for (i=0;i<x;i++)
   {
       plain=pc3encode(tab[i]);
       tab[i]=tab[i]^plain;
   }
  i=i-1;
   for (z=1;z<=((x+1)*10);z++)
   {
       plain=pc3encode(tab[i]);
       tab[i]=tab[i]^plain;
       i=i+1;
       if (i>=x) i=0;
   }

   reste=lngkey%2;
   cle=lngkey/2;
   if (reste!=0) cle=cle+1;

   for (z=0;z<128;z++)
   {
    b[z]=0;
   }

   y=0;
   for (z=0;z<=(cle-1);z++)
   {
    if ( (z==(cle-1))&&(reste!=0) )
     {
       b[z]=(tab[y]*256)%65536;
     }
    else
     {
       b[z]=((tab[y]*256)%65536)+tab[y+1];
       y=y+1;
     }
    y=y+1;
   }

   for (z=0;z<x;z++)
   {
     key[z]=0;
     tab[z]=0;
   }

   r=0;
   a=0x015a4e35;

     for (index2=0;index2<=(cle-1);index2++)
     {
       for(z=0;z<=index2;z++)
       {
       stream(&r,&index2,&a,b);
       }
     }
   return(0);
}

int main()
{
  unsigned int longueur,y;
  unsigned char code[33];
  FILE *in,*out;
  short c;

  strcpy(code,"abcdefghijklmnopqrstuvwxyz012345"); /* the PASSWORD */
  longueur=32;

  /* init the key */

  pc3init(longueur,code);

  if ((in=fopen("input.bin","rb")) == NULL) {printf("\nError reading file INPUT.BIN !\n");exit(0);}
  if ((out=fopen("output.bin","wb")) == NULL) {printf("\nError writing file OUTPUT.BIN !\n");exit(0);}

  /* encrypt the file INPUT.BIN and write it to OUTPUT.BIN */
  while ( (c=fgetc(in)) !=EOF )
  {
   fputc(pc3encode(c),out);
  }

  fclose(in);
  fclose(out);

  if ((in=fopen("output.bin","rb")) == NULL) {printf("\nError reading file OUTPUT.BIN !\n");exit(0);}
  if ((out=fopen("plain.bin","wb")) == NULL) {printf("\nError writing file PLAIN.BIN !\n");exit(0);}

  /* init the key with the same parameters as the encryption key*/

  strcpy(code,"abcdefghijklmnopqrstuvwxyz012345"); /* the PASSWORD */
  longueur=32;

  pc3init(longueur,code);

  /* decrypt the file OUTPUT.BIN and write it to PLAIN.BIN */

  while ( (c=fgetc(in)) !=EOF )
  {
   fputc(pc3decode(c),out);
  }

  fclose(in);
  fclose(out);
  return(0);
}