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     14 January 2001
     Update: 14:08 GMT
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   CPRM on hard drives - IBM takes a spin
   [6]By: [7]Andrew Orlowski in San Francisco
   Posted: 24/12/2000 at 11:08 GMT
   A squadron of heavily armed IBM spin bombers left their hilltop base
   at Almaden, Ca at the end of last week. Their destination - Vulture
   Central. Their mission - to disarm public outrage at the proposed
   inclusion of CPRM copy control mechanisms into hard disks. The bombers
   were loaded with a good-natured arsenal of flattery, non sequiters,
   and laser-guided hand waves.
   Normally we'd send such missives straight to the bit bucket, but on
   this occasion, they're worth airing. Not just because this is spin of
   a subtle quality that we rarely hear - although it is - but it gives
   the best clue yet of how the industry will attempt to massage public
   concern on the subject. And to be forewarned is to be forearmed, we
   Before we get stuck in, however, acquaint yourselves with the CPRM
   proposals at first hand. The T.13 committee makes documents freely
   downloadable, and the two you really want to read are the latest
   [8]Content Protection of Recordable Media proposal and a 24-slide
   [9]Presentation by the same author, Jeff Lotspiech of IBM's Almaden
   Lab, which gives a bird's eye view of the subject. Another useful
   document is [10]an article in IBM Research's own house magazine Doh!
   [shouldn't that be Think - ed.] where CPRM's twin brother CPPM is
   discussed. This explains the mechanics of CPRM in layman's terms, but
   of how sophisticated the system is, and the challenge it presents to
   would-be hackers.
   But as you peruse the T.13 documents, ask yourself "Why is this even
   here?". ... And ask yourself the same question at regular intervals in
   the next few paragraphs.
   Go away folks, there's nothing to see
   "What they[4C] 're asking for in the ATA standard is not to
   incorporate content protection but to reserve some space in the spec
   for calls or functions that content protection that others could call
   upon," insists Mike Ross, spokesman for IBM's Alamaden Labs. But
   Lotspiech's cryptographic structure for CPRM is well defined already.
   The system interface is also defined in the CPRM technical proposal:
   in excruciating detail, as you can read in the references above.
   "CPRM is NOT tied to a fixed location on the disk," says Ross. "The
   Media Key Block can be placed anywhere that is convenient for the
   Wow, we thought: this guys's good. This guy's really good.
   But it's nonsense of course, and what can most charitably described as
   a straw man. Recall that there are two areas that CPRM can be said to
   reside - and here, use page 10 of the presentation above. The Media
   Key Block (which is most of that megabyte) is in a read-only area, and
   the Media Unique Key (which uniquely identifies the disk) is in a
   "hidden area". Both are what is called "vendor space" - the part that
   handles out of bounds sector swapping, and that's separate from the
   file system itself. It's a puzzling assertion, as we don't remember
   claiming that CPRM is tied to a physical location on the disk
   ourselves, but we did point out - and the specification points out -
   that CPRM physically locks signed media into a given location, driving
   a bus through the concept of file system abstraction.
   Hard disk experts tell us that at a device level, when issuing a write
   command you don't really know where you putting it, so there's a
   couple of levels of abstraction going on here. But CPRM in ATA breaks
   one of them, and that in itself is only the beginning of where the
   proposal is so fundamentally redraws the computer landscape.
   As Ross confirms: "All of the content files can be moved, copied, even
   renamed -- in their encrypted form. CPRM only insures that the
   protected files are played or viewed only by compliant software or
   devices" [our emphasis, natch].
   As for the short-term damage to commodity RAID, file optimisation,
   backup, and potentially imaging software too, Ross says "These are
   good points, these issues will have to be addressed in the marketplace
   and you're absolutely right - but these have not even been discussed
   Porky packets
   IBM insists that the proposals are intended to secure content on
   removable media, and that hard disks aren't really the target:
   although in Ross' words "Would a hard drive benefit from the calls
   requested here? Absolutely - so you could take that to the next step"
   But let's look at the context for a second. There's ATAPI - the spec
   for removable media, and then there's ATA - the spec for hard disks.
   They're closely related, and share semantical similarities, but also
   differ significantly. ATAPI is a packet format. What's being proposed
   isn't ATAPI - it's ATA, and contains information that ATA devices
   need, but that ATAPI devices don't. In other words, the specification
   can be rolled into fixed, ATA devices right off the bat.
   So how mandatory are these specifications? Dave Anderson of the Object
   Based Storage Device group - he's also Seagate's storage architect,
   but was speaking to us with his OBSD hat on - points out that not all
   of the SCSI command set has been implemented. Even where the commands
   have obvious benefits. It's a good point, but it's also worth
   remembering that the SCSI design philosophy (do more) differs from ATA
   mores (keep it simple) with the consequence that the ATA spec is much
   more closely adhered to by manufacturers. It's a far simpler spec, and
   being a mass market, doesn't tolerate wibbles. CPRM's backers point
   out that it's an optional mechanism, and needs to be turned on
   explicitly: for example a "compliant" CPRM drive may yet be programmed
   to reject calls by compliant applications to write secure media to
   The T.13 committee next meets in Irvine in February. It's already seen
   three drafts of CPRM, which may give opponents of the scheme hope that
   it can be delayed further. Equally, we suspect, CPRM's backers may
   hope that the pre-Xmas furore will be forgotten as we nurse new
   century hangovers in just over a week. But CPRM in ATA poses
   short-term problems for several classes of current software and IT
   practices, long-term threats to accepted consumer free use practice
   and to basic computer science principles such as file system
   abstraction, and could particularly divisive for free software in
   particular - as Richard Stallman has pointed out. In short, it has the
   potential to make the Clipper Chip saga look like a pre-show warm-up,
   and we wouldn't bet on this story going away anytime soon. As the
   Grinch discovered: "Oh, the noise! That's one thing he hated! The
   Related stories 
   [11]Stealth plan puts copy protection into every hard drive
   [12]Linux lead slams 'pay per read' disk drive plan
   [13]Copy protection hard drive plan nixes free software - RMS
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