Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.1 6/24/83; site iuvax.UUCP
Path: utzoo!linus!vaxine!wjh12!genrad!decvax!harpo!ulysses!burl!we13!ihnp4!inuxc!iuvax!notes
From: notes@iuvax.UUCP
Newsgroups: net.micro
Subject: Software protection in software - (nf)
Message-ID: <347@iuvax.UUCP>
Date: Sat, 14-Apr-84 01:04:22 EST
Article-I.D.: iuvax.347
Posted: Sat Apr 14 01:04:22 1984
Date-Received: Sun, 15-Apr-84 01:56:50 EST
Sender: notes@iuvax.UUCP
Organization: Indiana University
Lines: 35

#N:iuvax:400012:000:1431
iuvax!apratt    Apr 13 21:53:00 1984


One poster on the subject of software protection suggested that a
serial number could be associated with each computer or company, and
that programs could be written to check that serial number and autodial
the police if it didn't match (that last is a joke...).

This would be a good scheme except for two things:  the fact that the
hardware with the code in it could be copied and installed in another
machine, and the fact that somebody could modify the program in such a
way that the check were not made.  Don't say that the program can
checksum itself to prevent tampering: that check, too, can be
circumvented.

Any software protection scheme can be prevented if the user (read:
potentially determined pirate) can see and modify the instructions, and
in Von Neumann machines, the whole POINT is that the code can be read
and modified.

One protection scheme which, I am told, the US Government employs is to
PHYSICALLY seperate the code (text) and data busses WITHIN THE
PROCESSOR.  In this way, no user has access to the programs which are
running, and so cannot read or change any of the programs that are in
"program text" memory.

As long as a user can get his hands on the program code, he can
circumvent and software protection scheme simply by inserting a "jump"
over the protective code, like a burglar cutting the door away from the
lock and swinging it open.

						-- Allan Pratt
					...ihnp4!inuxc!iuvax!apratt