[Gllug] [OT] CF card mp3 players?

[Richard Jones]

On Fri, Oct 15, 2004 at 12:59:54AM +0100, Mike Brodbelt wrote:
> SD presents a superset of the functionality of MMC. An MMC card
> basically contains addressable memory and a memory controller chip,
> IIRR, and most readers just present a USB mass storage interface to the
> host. SD is the same, with one addition - it also has a "protected"
> region for holding keys, which can be used to lock content to devices
> containing the correct keys.
> 
> As far as I understand/remember, SD implements the SDMI specifcation of
> CPRM. So, if you download an mp3 track using say, a mobile phone, the
> track will be encrypted, and a device-locked key stored in the protected
> region. This effectively locks the track to the original device, as only
> that has the correspondong key to get at the key needed to decrypt the
> data.

But how is this region "locked"?  Surely to decrypt the track you've
got to read the encrypted track and the key, and presumably the SD
card itself doesn't have any decryption technology on it, so that
means it must be the connecting device which reads the key ... in
which case you've got no security.  Is the reason that SD drivers must
be closed source mere security-through-obscurity?

Rich.

-- 
Richard Jones. http://www.annexia.org/ http://www.j-london.com/
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