On Tue, Sep 03, 2002 at 11:55:47PM +0100, Glynn Clements wrote: > > Yannick Gingras wrote: > > 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. It's taken as a given by those who understand computer security that if you don't control the hardware completely as well as the software, the software _can_ be broken. Even that's not always sufficient, as has been demonstrated by the people who have managed to crack the X-Box. Anything out in the users' hands can be cracked with sufficient resources. The trick is making sure that the 'sufficient resources' are higher than most will be willing to bother with. > > 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. True, though that only got one 'player key' by itself. CSS involved encrypting the disk with a single 'session key', then storing that session key on the disk once for each licenced 'player key'. That way if one player was broken like happened with the Xing player, later DVDs could be mastered without using that key, so the broken player would stop being able to play new DVDs. Of course, once one player key was broken, dealing with the rest became a known plaintext attack, and the rest of the player keys went down like a row of dominos. ---------------------------+--------------------------------------------------- Bryan Feir VA3GBF|"The professor holds the keys to the gates of Work:bryanat_private | knowledge; not to let the student in, but to let Home:jenoraat_private | him get out and on to better things." -- Leacock ---------------------------+---------------------------------------------------
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