Wiping Drive

L

Luc The Perverse

Hey I saw a bid rid request on a programmer site for a secure file deletion
utility.

I was wondering if such a thing could be written efficiently in Java - or if
cross platform stuff makes that almost impossible because you can't ensure
things we will be written before you rewrite, and you get no low level disk
access?
 
T

Tom Forsmo

Luc said:
Hey I saw a bid rid request on a programmer site for a secure file deletion
utility.

I was wondering if such a thing could be written efficiently in Java - or if
cross platform stuff makes that almost impossible because you can't ensure
things we will be written before you rewrite, and you get no low level disk
access?

It first depends on what they define as secure file deletion. If they
mean overwriting the contents of the file in a secure way, then I
suspect its just a matter of writing carefully picked bit patterns
across the file length X number of times. But the problem is you can not
necessarily guarantee that it write on the same sectors as the file
originally was stored. For example, some file systems move the physical
files around to prevent fragmentation. Others employ other techniques.
So to make a claim of secure file deletion you have to understand the
underlying file system supported and you have to use either the kernel
api, the fs driver or raw disk access directly

In any case, I think this rules out a pure java implementation, you
could use a jni implementation, but then you are not far off using a c
version instead. In any case the program is bound to the specific system
and file system so there is no added value in using java.

FYI, there are companies that specialise in dismantling a hard drive and
with special tools read data of individual physical sectors of the
actual discs in the drive. One company I know of, www.ibas.com, has been
able to read data of a disk sector where the data had been overwritten
ten times already. They sell a software tool that almost guarantees
secure deletion. That is why the military disposes of their most
sensitive hard disks with the help of an acid bath instead.

tom
 
L

Luc The Perverse

Tom Forsmo said:
It first depends on what they define as secure file deletion. If they mean
overwriting the contents of the file in a secure way, then I suspect its
just a matter of writing carefully picked bit patterns across the file
length X number of times. But the problem is you can not necessarily
guarantee that it write on the same sectors as the file originally was
stored. For example, some file systems move the physical files around to
prevent fragmentation. Others employ other techniques. So to make a claim
of secure file deletion you have to understand the underlying file system
supported and you have to use either the kernel api, the fs driver or raw
disk access directly

In any case, I think this rules out a pure java implementation, you could
use a jni implementation, but then you are not far off using a c version
instead. In any case the program is bound to the specific system and file
system so there is no added value in using java.

FYI, there are companies that specialise in dismantling a hard drive and
with special tools read data of individual physical sectors of the actual
discs in the drive. One company I know of, www.ibas.com, has been able to
read data of a disk sector where the data had been overwritten ten times
already. They sell a software tool that almost guarantees secure deletion.
That is why the military disposes of their most sensitive hard disks with
the help of an acid bath instead.

Sounds a little far fetched to me - especially from the perspective of a
software tool - maybe if they claimed to be able to do it in a clean room
with some special reader I would be more inclined
 
T

Tom Forsmo

Luc said:
Sounds a little far fetched to me - especially from the perspective of a
software tool - maybe if they claimed to be able to do it in a clean room
with some special reader I would be more inclined

I am sorry but I don't understand exactly what is it that you think is
far fetched?

tom
 
D

Dag Sunde

Luc The Perverse said:
Sounds a little far fetched to me - especially from the perspective of a
software tool - maybe if they claimed to be able to do it in a clean room
with some special reader I would be more inclined

What is far fetched? (There is two different statements above)

* Ibas have been able to read the data... Probably in a clean room
environment
with special hardware most assuredly.
* They sell a software tool that almost guarantees secure deletion.

....They *do not* sell a software tool that can read data that have been
overwritten 10 times... That would be kind of shooting themselves in the
foot, since they make a living out of data-recovery and restoration.

:)
 
L

Luc The Perverse

Dag Sunde said:
...They *do not* sell a software tool that can read data that have been
overwritten 10 times... That would be kind of shooting themselves in the
foot, since they make a living out of data-recovery and restoration.

I misread it then
 

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