Date   : Tue, 06 May 2003 22:00:40 +0000
From   : "W.Scholten" <wouter.scholten@...>
Subject: Re: BBC Micro Games Copy Protection

John Kortink wrote:

> >I thought the elite tape version was extremely easy to crack. I remember
> >the use of an IRQ routine to flip the last block bit for the last file,
> >but nothing else stands out in my memory as being difficult (I've still
> 
> That was only the first hurdle. Then the tape could be
> copied, yes. But it was followed by a very varied array
> of copy-to-floppy defenses (I remember counting at least
> 10 different ones, and that stuck in my mind because most
> other games at the time relied on only a few minor or major
> hurdles).

That bit flipping code was what I remember most of all, but that doesn't
mean that that removing that was all I did ;)

I have the complete disassembly at hand that I studied/made at the time,
and I noted at the time what all the sections do (EORing, checksums,
pushing data on the stack, then executing that data by jumping to page
1, plotting dots, ellipse calculations etc etc). I removed and/or
disabled all the unnecessary junk code (ELITEdata shrunk to 13xx from
15xx IIRC, ELITEcode also shrunk from 50E8 to 50C0 also IIRC), so I'm
pretty sure I took care of everything (which I did primarily because it
was ugly! I think I placed the data after EORing in ELITEdata instead of
leaving the EOR code in etc, as I consider that part of the cracking job
(so I can easily disassemble/study data from all parts of the program)).
I'll dig up the files and have a look again sometime soon.


> >P.S. Was anyone else here disappointed as I was in the tape version of
> >Elite? No missions, very few ships, no military or mining lasers...
> 
> Yes. I bought the disc version lateron, just for the missions. :-(
> Of course, the extra stuff was really due to the advantages of the
> storage medium rather than a deliberate attempt to cripple the tape
> version.

I think it would have been not too difficult to first load in a file
with ship data in which one or two were chosen instead of one or two
others, then load in the rest of the code overwriting what was not used.
That would at least give more ships which was my primary irriation (as
they are all shown in the manual, not ever encountering many of these
types is rather annoying to say the least!)

Regards,

Wouter

-- 
BBC/atom/old magazine scans etc:
http://www.astro.livjm.ac.uk/~bbc/