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Re: Business models

Mads Bondo Dydensborg wrote:
> On Thu, 26 Apr 2001, Henningsen wrote:
> > >When they download the game from the website, you could have the server
> > >embed the date it was downloaded on into the executable...then *bang*
> > >three days later the game demands money.
> >
> > The server would have to write to the source files and recompile and send a
> > different exceutable to every user, right? Or is there a simpler way of
> > doing this?
> There is nothing wrong with changing an executable with e.g. sed.
> It is very ugly, yes, but it does work.
> The qkhack for Quake worked in this way. It changed the name of some
> libraries, thereby changing quake's mouse and keyboard input from using
> svgalib to using X. (With a bit of wrapper code in a special dll).
> However, as someone pointed out, it is as easy for the downloader to
> change the binary back - if he can find the code in the binary, that is.

You can fix that.

He'll easily find out where you placed the date code in the binary - just
download two copies on different days and look to see which bytes are

However, I would encrypt the date and embed the encrypted form in the file.
Since that's the date he downloaded the game, and not the date it expires,
and he doesn't have the encryption algorithm - there isn't much he can do
to insert a new encrypted date that would work to extend the life of the game.

Of course this only works in a closed-source setup otherwise you could just
dive into the source and comment out the entire date checking code.

A *really* clever scheme would be to encrypt the database with some kind of
code that requires a key to decrypt it.  Form the key by mangling todays'
date *and* a number provided by your web server and he'll have to visit your
site every day (or every week or whatever) in order to play.

Steve Baker   HomeEmail: <sjbaker1@airmail.net>
              WorkEmail: <sjbaker@link.com>
              HomePage : http://web2.airmail.net/sjbaker1
              Projects : http://plib.sourceforge.net

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