Where should I store my application's "activation" key?

Question

I've written an application and I'd like to add a registration key/serial number to it (I'm big on minimum inconvinience - ala #4 at this Eric Sink article). My question is about where to store the "activation" once the application has been registered. As I understand it, I have a trade-off between storing the key in a public place, where all users can read it (but which requires admin rights to save there) and storing a per-user activation (but then each user on the computer will have to activate independantly). That gives me two choices:

1. Some user, with local admin rights, activates the product. The activation is stored in HKLM, in the program files folder, or somewhere else where all users can read it, and the product is activated for all users.
2. A user (with or without admin rights) activates the product. The activation is stored somewhere user-centric (per-user app.config, HKCU, etc). The plus is that the user doesn't have to be an admin. The downside is that if there are 6 users who use the computer, each has to activate the product. They can each re-use the same serial, but they still have to enter it.

Is this really the trade-off? If it is, what have others done? As a developer, I'm used to people being a local admin, but in the real-world, I don't expect many of my corporate users to be local admins, which makes me lean towards option 2. Are computers not shared often enough that I shouldn't be concerned?

Again, I'm not asking about how to physically register a computer - I'm not worried about it. I'm only going to checksum the key provided and give the go-ahead, as I want to be as non-invasive as possible.

Answer 1

I would recommend a solution that does not require admin rights. Lots of users, especially in shared environments, won't have those rights and won't be able to find anyone with them conveniently.

Also, going forward a few years, I think it will be getting increasingly unusual to have admin rights on the computer you are using, as the security situation improves.

Answer 2

Registry seems to be an okay solution for business software. At least at where I used to work, regular user will not be a local computer administrator, so each installation will require local administrator account. This is a good thing since it will lessen the headache of your support staff from people installing just about everything in your business computing environment. The trade off is of course, user will be pissed that they can't install stuff or have to contact support to do it, but hey... :)

Other stuffs:

• USB / other type of dongle (ala old 3DMax)
• plain old text file (ala Garmin GPS software on mobile device)
• Encode them / rewrite the key into your binary or part of your binary (did this trick back in th old DOS days)
• Store them in your own db via web (ala EverQuest / other MMORPG games)
• Local key db (ala MathLab I think)