Slashdot Mirror
The Great Zero Challenge Remains Unaccepted
An anonymous reader writes "Not even data recovery companies will accept The Great Zero Challenge and only four months remain! We've all heard how easily data can be recovered from hard drives. We're told to make multiple overwrites with random data, to degauss drives and even physically destroy them just to be extra safe. Let's get the word out. The challenge is almost over! It's put up or shut up time. Can you recover the data?"
Although the drive has to be in a living system and not on the shelf, it's worth noting the cold boot attack
Not in this context because we're talking about how intentionally wipe the data from a drive, e.g. when you want to erase the data and dispose of the disk. The cold boot attack, although interesting, has nothing to do with recovering data from a drive after someone has attempted to destroy it, unless your implication is that someone would try to overwrite the header a split second before someone like the FBI breaks the door down. Even then, simply unmounting the volume will wipe the key from memory. If you have time to attempt an erasure you have time to unmount the disk. If you are in a situation where you have enough time to write zeros all over the drive, as in this challenge, you are certainly not at risk from the cold boot attack.
... it is merely old tech that is no longer relevant. In the old days of sloppy mechanical tolerances (and read-write heads), it was possible to leave traces that were misaligned with the main bits of the current data. With good custom drivers and software, it was often possible to recover some of this data.
This is of course no longer true what with much tighter tolerances, smaller and vertical magnetic domains, and so on. I think that is the point of this challenge.
It is likely that there is a hysteresis in the platter causing a "0" written on top of a "1" to be slightly "weaker" than a "0" written on top of a "0".
On old tape, this hysteresis was about 10%, and was actually visible with a magnetic loupe, so depending on s/n ratio, you could recover quite a bit, no pun intended.
The problem with a HDD is that the signal from the heads go through a lot of signal processing including Extended PRML or EPRML. There is also an algorithm like RZ to not have a long series of the same bit written physically. If you take the electrical output from the read head, you will have a big task reconstructing the data, even if there only good data.
The only places today that can analyze well what is read physically is at HDD manufacturers research lab, and probably using custom HW to read the platter that collects all the errors and offsets. For a recovery company to do this, they probably would have to invest millions of $$$, so they will not.
So bottom line is that you could send the drive in to Western Digital, and they could probably recover the raw data with about 90% accuracy. If that is enough for the error recovery to chew on, I am not sure, but here and there, long strings would be recovered. They can for sure give the exact probability for the recovery of a bit.
WD however does not have any incentives to demonstrate that wiping their drives with "0" is not sufficient. aux contrare, they may consider this an undesirable property. Therefore, the only ones that can recover this is unwilling.
So the challenge remains unaccepted.
don't cut it off www.mgmbill.org