Data Integrity vs. Not Copyable On Purpose

Sheffield, Robert L robert.l.sheffield at
Tue Jun 10 17:07:59 PDT 2003

* From the T10 Reflector (t10 at, posted by:
* "Sheffield, Robert L" <robert.l.sheffield at>

I can see how one might envision the application of this to copy protection, but that wasn't the intent when we drafted the proposal. As defined, legacy read commands work just fine, so if someone wants to read the data (even though it's "protected" by the DIF), it's available - the DIF is just not provided with the data. Think of the DIF information as an identifying tag of some sort that "matches" the data, both in terms of identifying it, and in terms of validating the content hasn't been corrupted. So IF you want to make sure the target fetchd what you requested, you can check the tag to see that it matches what you requested, and that it's consistent with the content. This is just like a coat check. The clerk could give you the wrong coat, but you'd be able to prove it was the wrong coat by showing him your claim ticket. A better analogy is lazer-inscriptions on precious diamonds. It doesn't keep them from stealing it, but if the jewler gives you your ring back and it d!
oesn't have the right inscription on the diamond, you know he didn't give you your diamond back. We're basically talking about authentication, not so much protection in the sense you've suggested.

That said, it might be possible to tweak the DIF proposal a bit to provide some sort of copy protection. The target would have to reject legacy read/write commands for DIF protected datablocks, and would have to withhold the read transfer for any datablocks tagged in a way that doesn't match the request. The problem then is to distinguish between illicit copy requests versus ligitimate error conditions. There's more work to do here to address the copy protection capability, and I really haven't thought through it enough to know if the DIF proposal might form a reasonable basis for it or not.

Bob Sheffield
Intel Corporation - CH6-333
Storage Components Division (SCD)
5000 W. Chandler Blvd
Chandler, AZ 85226-3699
Phone: 480-554-8597
Fax: 480-554-6617

-----Original Message-----
From: Pat LaVarre [mailto:LAVARRE at]
Sent: Tuesday, June 10, 2003 3:34 PM
To: t10 at
Subject: RE: Data Integrity vs. Not Copyable On Purpose

* From the T10 Reflector (t10 at, posted by:
* "Pat LaVarre" <LAVARRE at>
Thanks for the interest offline.  THREE clarifications:

1) My question restated:

I mean to ask for someone to draw a distinction between a file system confirming that it is reading something it wrote and a media player confirming that it is reading something that only an authorised writer wrote.

In my ignorance, I'm failing to draw that distinction, so I think we are again talking about copy protection, except I didn't hear anyone say so, so probably we're not, instead probably I'm just significantly ignorant near here, so I'm curious.  I'm familiar with people using "security" as a euphemism for "copy protection", I'm trying to establish if that is going on here or not.

2) My jargon:

Me, I would define both "copy protection" and "digital rights management" as meaning "making bits not copyable on purpose", though to my ear "digital rights management" implies a finer degree of control, like letting me reinstall Win XP seventy-seven times but not seventy-eight.  Those bits are sometimes copyable and sometimes not - they just aren't infinitely recopyable, despite being bits.

Sorry I slipped out of using the conventional jargon, I should have written "copy protection", rather than "not copyable on purpose".

3) My missing example:

I can't easily provide a widely familiar concrete example of making bits not copyable on purpose, because so far personally I've flatly declined to pay for intentionally crippled digital appliances.

Maybe a widely familiar example, if true as rumoured, would be the movies recorded on DVD's encoded to play only in U.K. players and not also in U.S. players.  I'm told I have to buy one player for when I am in the U.K. and another for when I am in the U.S., and swap out the players to match my disks, according to where I bought my disks.  Or I can buy two of every disk as well as two players, to get out of swapping players.  Seemingly this is an effective tactic of the movement against globalisation.

Pat LaVarre

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