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From: mort@ihuxn.UUCP (Dubman)
Newsgroups: net.micro.apple
Subject: DOS Protection (Re:Josh Siegel)
Message-ID: <565@ihuxn.UUCP>
Date: Sat, 3-Mar-84 21:28:59 EST
Article-I.D.: ihuxn.565
Posted: Sat Mar  3 21:28:59 1984
Date-Received: Mon, 5-Mar-84 00:43:19 EST
Organization: AT&T Bell Labs, Naperville, IL
Lines: 28

In response to your request:  I know 6502 like the back of my hand, and I am
fairly knowledgeable in direct machine language disk access, though I need to
brush up a BIT on the "raw data" (prenibbilized) format.

There are some really neat protection routines out there, like SPIRALING the
data (skipping half-tracks inward every quarter-revolution) and ALL SORTS of
insane schemes.  Personally, I don't bother to protect the arcade games that
I write.  I know that with a paperclip, an opened Apple II, and a neat little
disk program you can break into just about anything that does not access the
disk drive more than once.  And for everything else- either Locksmith,
Wildcard, or a Boottrace (can work every time) will copy/break it.

It depends.  If you are trying to just defer the novice from copying your
disk, four pokes and a DOS command, and a little program that sticks in a
couple of "ninety-sixes" and does a modified COPYA will make a disk that 
couple of "ninety-sixes" can make your program
virtually impossible to crack using normal copy programs.  I forget the loca-    
tion of the D5 AA 96 or whatever hex sequences make up the prolog and the
epilog for a data stream but if you change those then COPYA and all those
copiers that use RWTS will bomb.


-- 

Jonathan Dubman - care of:

		Mort Dubman		AT&T Bell Laboratories
		ihnp4!ihuxn!mort	Naperville, IL.