[Cryptography] Shredding a file on a flash-based file system?

[Bear]

On Thu, 2014-06-19 at 13:48 -0400, Perry E. Metzger wrote:
>  I must say I do *not*
> trust hard drives with built in encryption, because there is no way to
> test that they are working correctly.

I have never understood the threat model that these drives 
supposedly protect against.  

Under what circumstances would an attacker have the drive 
platters in hand, but not have access to the key which is 
stored in the drive hardware?  

If there were a worthwhile "encrypted drive" technology, the 
decryption routine, but not the key, would be built into the 
BIOS and the key would not be stored anywhere outside a 
volatile register - preferably one physically incapable of 
being read or written by any hardware at all other ythan a 
hardware channel from the keyboard (opened by the BIOS chip
only during bootup) and a hardware channel to the disk 
driver (opened by the BIOS only after bootup).

Under that system you could not do so much as read the boot 
sector without first entering the key at the local keyboard.

Of course, even if something that acts like that appears, 
which is unlikely, it will be a fake. Various agencies simply 
will not allow manufacturers to make a system that crooks 
cannot break into.  This is kind of like trying to keep 
houses and shops safe in a city where lockable secure doors 
are illegal.

				Bear