Re: how to store data in local safely
From: Jacob Heider (lord-jacob_at_comcast.net)
Date: Wed, 02 Jun 2004 09:02:32 GMT
On Wed, 02 Jun 2004 16:55:48 +0800, a posting issued forth from lgl...
> I have a problem now and want to get some help from you
> I am doing a DRM(Digital Right Management) system in linux, and now I am
> seeking a method for store data in local safely. for example:
> There is a license file for each digital content(mp3 file etc). Each time
> end users want play the mp3 file, he must first have a relative license
> file. There are various info in the license file. for example, there may be
> a element which specify the times the end user can play the mp3 file. What
> I want to do is:
> The fist time you play the file, I get the counter from the license file and
> store it locally. In future each time you play the file, I will decrease
> the counter untill it becomes zero. But how to make sure only my
> program(the player) can change the value, and the end user can't.
> I don't know whether SELinux will do.
> I will be very thankful if you can give me some advice.
Oy. Setting aside that this is antithetical to the Free Software
movement, and will be abhorrent to many Linux gurus, here is a (brief)
You must control the file. This means one of two things:
1) If this will only be used on systems where you are the administrator,
install your program suid, and have it modify a root-modifyable-only
2) If you don't control the computer, then the player must discourse
with a server under your control to get the license information
everytime the file is accessed.
Either way, it is unlikely anyone will use your product unless
absolutely required to. Nobody likes DRM, and legel constraints are
stronger, anyway. If your material is of sufficient value, someone will
break your security. Spend your time finding a good copyright lawyer,