the myths of "securely wiping harddrives". It is all bogus.. at least with regular harddrives.
Here is where it came from:
Back in the days of magnetic tapes, when you wiped them or taped something over them, the original signal was not lost but merely dampened. So you could get parts of the original signals back. But that was ANALOG signals. Not DIGITAL. There was ONE paper on this issue that hypothesized it might be possible to do this with harddrives. All government standards on securely wiping data are based on this.
Now to reality: Researchers have put the claims of this old paper to a test and published their findings. They actually were able to restore a single bit with a chance of 56% (0.56). That means they could restore two consecutive bits with a chance of 0.56*0.56=0.31 (31%). Probabilities multiply. Now you do the math of probability of restoring a single byte (8 bits) let alone a megabyte of data. A hint: .56^8=0.0096.
Here's the paper:
http://www.springerlink.com/content/408263ql11460147/
And here's the original paper that started the myth:
http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html
Also: There is always one point to consider. Think about how much your data might be worth and adjust your methods accordingly. If you data is worth thousands of dollars just shred the drive byond recognition. If you care about keeping the drive your data can't be worth that much and zeroing it out is definately enough. No one was ever able to restore any usable data from a drive that has been zeroed out. I hereby state that anyone who gives me prove to the contrary will receive a reward of $1000.
AreWeThereYeti promoted this comment
My favorite:
Alternative viewpoint:
- It is possible even with a single pass wipe to possibly recover data from a drive and may be possible with a three pass wipe. The reason being that as the drive warms up the exact placement of data is slightly skewed and when you do the most basic wipe of data you may not overwrite all of the space giving the most remote possibility of data recovery. To do this sort of recovery though takes some very advanced work. Your average person may not have access to the means necessary to pull this off. Your best option is complete drive destruction or degaussing as mentioned in the blog. for the home user you can come by doing a 7 pass wipe with the drive warmed up to room temperature and then while the drive is running put a very strong rare earth magnet on top of the drive once the drive is outside the case with only the power connected. This is milage may very sort of stuff.
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