 yannick gingras wrote what do you mean by cd key or the like i presume that of was a typo and what do you mean by unbreakable of was a typo unbreakable would mean here that no one even previously authorised entity could use the system without paying the periodic subscription fee you need to be far more explicit about the problem which you wish to solve and about the constraints involved it could be an online system that work NUMBER offline but poll frequently an offsite server no mass production cds maybe mass personalised d l like sun jdk nothing is fixed yet we are looking at the way a software can be protected from unauthorized utilisation is the use of trusted hardware really worth it answering that requires fairly complete knowledge of the business model but in all probability no it isn t usually worth it so it comes down to how difficult you want to make the cracker s job if the product requires occasional authentication simple copying won t work the product has to be cracked in which case the issue is whether you re actually going to enter into battle with the crackers or just make sure that it isn t trivial a lot of it comes down to your customer base teenage kids tend to be more concerned about cost and less concerned about viruses trojans and so more willing to use warez fortune NUMBER corporations are likely to view matters differently does it really make it more secure yes software techniques will only get you so far actually the same is ultimately true for hardware but cracking hardware is likely to require resources other than just labour almost anything can be reverse engineered but it may be possible to ensure that doing so is uneconomical look at the dvds iirc css was cracked by reverse engineering a software player and one where the developers forgot to encrypt the decryption key at that glynn clements glynn clements virgin net 