Dev:Tweak DRM

Building tweak DRM means building technical measures to control access to using a tweak you made, especially to prevent access by people who were supposed to pay for it but didn't, aka pirates. (DRM stands for digital rights management.)

Philosophical advice
Many developers choose to skip working on DRM for their paid tweaks and instead spend that time on making a great piece of software with lots of marketing and good support. Almost all DRM systems get cracked; many people who crack software have more free time than you do.

If you choose to implement DRM, you need to build it in a way that preserves access for legitimate users even if your DRM system fails. If your server goes down (and it'll inevitably go down), or if other mistakes happen, that must not prevent access to your product for people who have purchased it. saurik is willing to block purchases of Cydia Store products with faulty DRM, and the default repositories (especially BigBoss) also don't consider faulty DRM acceptable.

Some advice from saurik:

"DRM...increases the risk of your product receiving complaints, complaints that will translate into your vendor account no longer being trusted and your products being blocked from sale. This instead must be viewed as a tradeoff that you must consider."

"I do not consider hard DRM checks that happen during package scripts acceptable. For various reasons (related to how other packages that modify things related to network access are implemented) it cannot be assumed to be the case that Cydia still has working Internet access during the package installation phase (all packages are downloaded before this phase begins, which then happens as a semi-atomic unit)."

"However, the entire idea of having a DRM system that doesn't let the user use the product they just purchased unless your server is working at that very first instant is fundamentally flawed: even simple networking glitches or inevitable hardware failures lead to situations where users can't enable their purchases. You thereby really need some kind of "leniency" or "grace period" in your implementation to be acceptable."

"One common way of getting most of the way there is simply to implement a trial period for the product: the trial period tends to act as a buffer, decreasing the number of people who experience the failure (as most people who ever purchase at all actually purchase quite quickly and do not wait for the product to entirely expire). A more epic implementation involves a model where the system gives the user a few hours of grace."

Technical advice
You can add some advice here about writing good DRM!

Cydia Store Integration and crack prevention might be helpful articles.

You can also ask experienced developers for advice on this. One suggestion:

I've used a few different lightweight forms of DRM that don't interfere with User Experience at all, most of which have been unsuccessful (only delaying the inevitable). But there are a few schemes that can be successfully implemented (and so far moderately unbeaten) with appropriate use cases of the tweak. Message me on twitter (@apocolipse269) or IRC (apocolipse on ircsaurik, freenode, chronic-dev, etc) and I can offer some advise. -Apocolipse