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From: lippin@ragu.berkeley.edu (The Apathist)
Newsgroups: comp.sys.mac.programmer,comp.protocols.appletalk
Subject: Re: Idea for painless copy protection
Message-ID: <1991Jan27.214310.3870@agate.berkeley.edu>
Date: 27 Jan 91 21:43:10 GMT
References: <1991Jan27.144523.20674@phri.nyu.edu>
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Recently roy@alanine.phri.nyu.edu (Roy Smith) wrote:
>	When the program starts up, it installs something which listens for
>broadcast packets to a specific port (my knowledge of appletalk is sketchy,
>but this is easy to do in IP and I'm assuming AT has some similar
>mechanism).  The program then sends out a broadcast packet to that port and
>listens for any responses.  The responses it would get back would contain
>the serial number of other copies of the program installed elsewhere on the
>same AT network.  If any S/N matched that of this copy, it would refuse to
>run.

First, this can be streamlined to cut down on network traffic: put the
serial number of the just-starting copy in the broadcast packet, and
have the others reply only if their numbers match.

Several current products use a scheme like this.  With most, the copy
protection is innocous during ordinary use, although a few, through
sloppy programming, introduce a noticeable network load.

There are problems, however.  A legitimate user may be unable to start
the program because someone else is running with his serial number.
On a large network, it may be difficult to track down the offender.

Network managers must keep track of where all the serial numbers are
being used -- if one copy is destroyed, they have to reinstall it with
the right serial number.

On some networks, notably those in university labs, people move from
one machine to another often, and it's not practical to buy a copy for
every machine unless the program is very popular.  These people would
prefer that you limit the number of copies in use, but in a way that
doesn't specify which ones must be used.

If the serial number is embedded in the program, rather than entered
by hand, more problems arise.  Backups must be kept of each of the
original disks.  The program can't be distributed through a server --
the right set of floppies must be delivered to each computer.  And
site licenses become awkward, as you must deliver a set of disks for
every copy licensed.

A solution to some of these problems is to give each copy a file
containing a list of serial numbers it can attempt to register under.
The program could try each in turn, listening for complaints from the
previously running copies.  This file could be the same for everyone
on the network, or some people could have private numbers present only
in their file.

					--Tom Lippincott
					  lippin@math.berkeley.edu

		"Self meets Self at a cocktail party,
		 exchanges business cards with Self,
		 and thus becomes Self Proper."
					--Jim Bolin