DRMs vs internet privacy (Re: Ross's TCPA paper)

[Adam Back]

On Wed, Jun 26, 2002 at 03:57:15PM -0400, C Wegrzyn wrote:
> If a DRM system is based on X.509, according to Brand I thought you could
> get anonymity in the transaction. Wouldn't this accomplish the same thing?

I don't mean that you would necessarily have to correlate your viewing
habits with your TrueName for DRM systems.  Though that is mostly
(exclusively?) the case for current deployed (or at least implemented
with a view of attempting commercial deployment) copy-mark
(fingerprint) systems, there are a number of approaches which have
been suggested, or could be used to have viewing privacy.

Brands credentials are one example of a technology that allows
trap-door privacy (privacy until you reveal more copies than you are
allowed to -- eg more than once for ecash).  Conceivably this could be
used with a somewhat online, or in combination with a tamper-resistant
observer chip in lieu of online copy-protection system to limit
someone for example to a limited number of viewings.

Another is the "public key fingerprinting" (public key copy-marking)
schemes by Birgit Pfitzmann and others.  This addresses the issue of
proof, such that the user of the marked-object and the verifier (eg a
court) of a claim of unauthorised copying can be assured that the
copy-marker did not frame the user.

Perhaps schemes which combine both aspects (viewer privacy and
avoidance of need to trust at face value claims of the copy-marker)
can be built and deployed.

(With the caveat that though they can be built, they are largely
irrelevant as they will no doubt also be easily removable, and anyway
do not prevent the copying of the marked object under the real or
feigned claim of theft from the user whose identity is marked in the
object).


But anyway, my predictions about the impending collision between
privacy and the DRM and copy protection legislation power-grabs stems
from the relationship of privacy to the later redistrubtion
observation that:

1) clearly copy protection doesn't and can't a-priori prevent copying
and conversion into non-DRM formats (eg into MP3, DIVX)

2) once 1) happens, the media cartels have an interest to track
general file trading on the internet;

3) _but_ strong encryption and cryptographically enforced privacy mean
that the media cartels will ultimately be unsuccessful in this
endeavour.

4) _therefore_ they will try to outlaw privacy and impose escrow
identity and internet passports etc. and try to get cryptographically
assured privacy outlawed.  (Similar to the previous escrow on
encryption for media cartel interests instead of signals intelligence
special interests; but the media cartels are also a powerful
adversary).

Also I note an slip in my earlier post [of Bear's post]:

| First post on this long thread that got it right.

Ross Anderson's comments were also right on the money (as always).

Adam

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