> That's why there are economically valuable DRM systems (BluRay's BD+ is an example here). All you have to do is push attacker cost across a threshold (for ins

> That's why there are economically valuable DRM systems (BluRay's BD+ is an example here). All you have to do is push attacker cost across a threshold (for instance with BD+, that's keeping titles secure past the new release window) to make a defense in depth control valuable. A really good example of this is Spyro 3: The developers set up a system of overlapping checksums (which could in turn bet part of the data being checksummed by other, overlapping, checksums) so that it was virtually impossible to change even a single bit without failing the test. It was eventually cracked, as the check only ran at boot time (it required 10 seconds of disk access, and adding 10 seconds to every loading screen in the game would have been unacceptable), which meant it took over two months for pirates to get a crack working (unusual for the time). And since most game sales come in the first two months... But that's really just me using this as an excuse to share a bit of technical trivia.