I am afraid you are confused.
SSL and safely storing bank documents are jobs for encryption and this works very well. Basically you send a lockable chest to your bank but retain the key, they put your documents into it, close the lock, and send it back. Ensuring that only your key can open it. This is absolutely vital to modern society, but isn't a type of DRM.
DRM usually requires encryption, but also something else. The content producers send their content in a locked box and then try and send the key to your computer in a way where the computer can use it open the box and play back the content but you can't use it to open the box and take the content out. This is obviously logically impossible, which is why you are always hearing of DRM schemes being broken just to watch a film (conversely if you could break a modern encryption system you could literally steal all the money in every bank in the world).
So logically you can't actually implement DRM in closed source software, but with sufficient obfuscation you can get close (Intel literally burns some of the key into a special chip on your motherboard which makes finding it extremely hard). If you are open about what you code is and dose, that includes telling people where you hare trying to hide the key, making the game of hide and seek a bit shorter.