[thelist] You can play a song but you can't download it

Phil Turmel philip at turmel.org
Fri Mar 4 07:08:21 CST 2005


Ken Schaefer wrote:
> Stephen is both right and wrong. Using current DRM technology, one can
> certainly stop users from making digital copies of documents (including
> music). Without the appropriate license key, the music can't be decrypted.
> Whether or not the content can be intercepted between server and player is
> mostly irrelevant - it isn't useful to anyone.
> 
> However there is nothing to stop analogue attacks - you can always copy a
> document down by hand, or snap a picture using a camera. Likewise you can
> hold a tape recorder up to the computer speakers and make a copy that way.

Actually, Stephen is right.  Any music played on a standard sound card 
must be decrypted by the player software (whether streamed or not) 
before passing it to the sound card driver.  At that point, its an 
uncompressed digital sound data stream.  Hacking into that depends on 
the operating system (trivial in Linux, obscure in Windows), but the 
data stream is there.

http://www.oreillynet.com/pub/wlg/3517

Even using the signed driver enforcement tools in Windows can be 
defeated by running Windows on top of VMware and writing a rip driver in 
VMware.

This inherent vulnerability is pushing the develepment of DRM-enabled 
hardware in the sound and video subsystems. (Not there yet.)  When that 
succeeds, DRM will be real.

In the meantime, DRM does succeed in weeding out the casual ripper.

Phil


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