It applies to just the 3GS, so far anyway. ECID is still relevant, even if you have a jailbreak, because you cannot downgrade if you are on a stock firmware and do not have a decrypted copy of the images. A bad example would be if you were jailbroken, which may rely on an exploit in the 3.0 7A341 iBoot. If your phone came stock 3.0.1 or you updated to a stock 3.0.1, you would (in theory) not be able to downgrade to 3.0 again without a decrypted copy of your images. So, if your phone came 3.0 stock and you jailbroke it, then updated to stock 3.0.1 without a dump of your images, you're potentially stuck. If you bought a phone with 3.0.1 on it and the bug was fixed (this is of course, assuming it only exists in the 3.0 7A341 iBoot), you were done when you purchased the phone. Other potentially dangerous stuff is SEPO, which Apple could potentially use in tandem with different batches of devices. Say from week X to week Y have a vulnerability (because they shipped with a vulnerable firmware), the next batch, week Z and week A, could be altered to have an updated epoch. If a vulnerable image (say an image from the current firmware, 7A341) has a different epoch (one older than the epoch defined on the phone), the image won't run. Nothing else has to be updated really, just the epoch needs to be changed. This means no new bootrom has to be shipped. I do not know where the epoch information is stored (I assume in the NOR), but it should be easy to update, since there are already two different values for the iPod 2G. Remember the whole 2.1.1 iBSS not liking newer devices? I believe that whole fiasco may have been caused by the new epoch, but this hasn't been explicitly stated by any Dev Team member. I don't know if brute force is really an acceptable route, since I assume Apple would not be dumb enough to use a key that weak. The whole server thing kind of seems weird to me, because that means the phone relies on Apple's servers, which is somewhat dumb. It would make a lot more sense if the process was done on-device and the image was modified by iTunes, but there are little details on the whole process. Hopefully we'll see more details emerge soon enough.