Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!chinacat!woody
From: woody@chinacat.Unicom.COM (Woody Baker @ Eagle Signal)
Newsgroups: comp.lang.postscript
Subject: Re: Encrypting portions of PS file
Summary: here you go
Message-ID: <1577@chinacat.Unicom.COM>
Date: 13 Sep 90 22:33:06 GMT
References: <1660@shodha.enet.dec.com>
Organization: a guest of Unicom Systems Development, Austin
Lines: 201

In article <1660@shodha.enet.dec.com>, p_davis@epik.enet.dec.com (Peter Davis) writes:
> 
> I've noticed that font files, from Adobe at least, typically contain some
> preliminary stuff in plain old "readable" PostScript, but then the actual glyph
> definitions appear to be encoded in some way.
> 
> I'd like to encrypt the prolog of PostScript files my application in generating,
> and then revert to plain text PostScript for the remainder of the file.  Does
> anyone know if this is possible?  How?
> 
> Thanks.
> -pd


#include "stdio.h"


/*
	routine takes an encrypted eexec file and creates a
	decrypted eexec file.  First cut is much simpler than
	the full decryption would be.  Full decryption will handle
	multiple keys, and have the flag to encrypt or decrypt things.
*/

FILE *infile,*outfile;

main(argc,argv)
char *argv[];
int argc;
{
int first =4;
int state=0xD971;
int c;
char decrptd;

	if(argc !=3)
		{
		printf("usage:  decrpt infile outfile\n");
		exit(0);
		};
	infile=fopen(argv[1],"rb");
	outfile=fopen(argv[2],"wb");
	
	while(fscanf(infile,"%2x",&c)>0)
		{
	/*	if(first !=0)	
			{
			first--;
			}
		else
			{ */
			decrptd= c ^ (state >>8);
			if(first !=0)
				{
				first--;
				}
			else
				{	
				fputc(decrptd,outfile);
				}
			state=state + c;
			state=state * 0xCE6D;
			state=state + 0x58BF;
		/*	} */
		}
	fclose(infile);
	fclose(outfile);	
}				
		
/* Quickie to convert postscript from stdin to eexec format on stdout */

#include "stdio.h"

static unsigned short buffer = 0xd971;
static unsigned long startup = 0xac7252f3; /* 00000000or whatever you want */

main(argc,argv)
char *argv[];
int argc;
{
  unsigned char input;
  unsigned char output;
  int init = 4;
  int i;
  int result;
  FILE *infile,*outfile;

	if(argc !=4)
		{
		printf("usage: encrypt startkey(long hex) infile outfile\n");
		}
	infile=fopen(argv[2],"r");
	outfile=fopen(argv[3],"wb");
	sscanf(argv[1],"%lx",&startup);
		
  fprintf(outfile,"%08lx",startup);
  for (i=0;i<4;++i)
    {
      input = (startup >> ((3-i)*8));
      buffer = (input + buffer) * 0xce6d + 0x58bf;
    }  

  for(;;)
    {
      for (i=0;i<(32-init);++i)
        {
          input = result = fgetc(infile);
          if ((int)result == EOF)
            break;
          output = (input ^ (buffer>>8));
          buffer = (output + buffer) * 0xce6d + 0x58bf;
          fprintf(outfile,"%02.2x",output);
        }
      init = 0;
      fprintf(outfile,"\n");
      if ((int) result == EOF)
      break;
    }
    fclose(infile);
    fclose(outfile);
}

/* Quickie to convert eexec format from stdin to postscript on stdout */

#include <stdio.h>

/* Written by Carsten Wiethoff 1989 */
/* You may do what you want with this code, 
   as long as this notice stays in it */

static unsigned short buffer = 0xd971;

main()
{
  unsigned int input;
  char output;
  int ignore = 4;
  int result;

  do
    {
      result = scanf(" %2x",&input);
      if ( (result == EOF) || (result == 0) )
        break;
      output = input ^ (buffer>>8);
      buffer = (input + buffer) * 0xce6d + 0x58bf;
      if ( ignore > 0 ) 
        {
          ignore--;
        }
      else
        {
          printf("%c",output);
        }
    } while (1);
}


/* Quickie to convert postscript from stdin to eexec format on stdout */

#include "stdio.h"

static unsigned short buffer = 0xd971;
static unsigned long startup = 0xac7252f3; /* 00000000or whatever you want */

main()
{
  unsigned char input;
  unsigned char output;
  int init = 4;
  int i;
  int result;

  printf("%08lx",startup);
  for (i=0;i<4;++i)
    {
      input = (startup >> ((3-i)*8));
      buffer = (input + buffer) * 0xce6d + 0x58bf;
    }  

  for(;;)
    {
      for (i=0;i<(32-init);++i)
        {
          input = result = getchar();
          if ((int)result == EOF)
            break;
          output = (input ^ (buffer>>8));
          buffer = (output + buffer) * 0xce6d + 0x58bf;
          printf("%02x",output);
        }
      init = 0;
      printf("\n");
      if ((int) result == EOF)
      break;
    }
}

Cheers
Woody