Easy to do, the keys are like right next to each other.

There, FTFY.

OK, mine is hunter2

It'd probably be less painfull if you got it made of cardboard.

Burma Shave

It may be impossible to make a theoretically unbreakable device, but that doesn't mean it's practically breakable.
You say yourself that it might take 10,000 years to get the correct key, so if the useful life of the device is say 10 (or even 100) years, it is still practically unbreakable.
And if you can make a device that takes 10,000 years to bruteforce, you can make one that takes 10,000 universe lifetimes...