sign7800 1.0

Short:        Generator of a valid digital signature for an Atari 7800 cartridge
Author:       Bruce Tomlin. Amiga port by Wojciech Pasiecznik/Voy/SSG^Dial^SWAT
Uploader:     Wojciech Pasiecznik/Voy/SSG^Dial^SWAT (voydial wp pl)
Type:         util/crypt
Version:      1.0
Requires:     MC68000+, ixemul.library
Architecture: m68k-amigaos

This program will generate a valid digital signature for an Atari 7800
cartridge ROM image.

The code was created by hand-decompiling the original 7800 encryption
program for the Atari ST into plain C code, so it does not rely on any
external libraries and should compile for almost any operating system
with no muss and no fuss.


To run it:
==========

   sign7800 -t filename   to test for a valid existing signature only
   sign7800 filename      to generate a signature printed to stdout
   sign7800 -w filename   to generate a signature and update the image

'Filename' is the name of the file with the cartridge data in it.  It
must be a binary file, with a size that is a multiple of 4K bytes.  An
extra 128 bytes is allowed, so that you can use it with a .A78 file.

The '-t' option only tests to see if an existing signature is valid.

The '-w' option causes the file to be updated with a new signature if
it was not aready valid.  A write will not happen if there is a problem
with $FFF8, $FFF9, or the reset vector, or if there is already a valid
signature in the file.  Even with an already valid signature, a new
signature is still computed and printed to stdout.

WARNING:  using the '-w' option should be safe if your file is really a 7800
cartridge image, but if it isn't, there is a possibility that data loss
to the last 128 bytes of the file could occur!  Be sure that you have a
backup copy of or can re-create whatever file you use with the '-w' option!