[migpwr]

Similar protection schemes existed with old dongle protected programs as well. Some were made nearly uncrackable because of how many checks were littered throughout the app. Most crackers wouldn't bother with patching every single location within the application and gave up on it.

[eneveu]

Yes. A few days ago, an interesting article on this very subject was (re-)posted on HN (written in 2001!): http://news.ycombinator.com/item?id=1156481 http://www.gamasutra.com/view/feature/3030/keeping_the_pirat...