Question on shredding a terebyte drive

[Les]

Earlier on in one of the threads, someone compared encryption with an
envelope.  That is pretty good.  You know the information is in there,
but the only way to get it is to open the envelope.  The question is how
long does it take to open the envelope.  No encryption is unbreakable.
The value of encryption is how long does it take to break it.  One
benchmark that is often quoted is a "bruteforce attempt".  Although it
is not literally a every combination of input attempt, it is quite
similar.  If a single very high speed computer were used, and the
algorithm was known or could be guessed, how long would it take to
retrieve the message?  This is those long years you see published.  
The purpose of encryption is simply to make the data harder to retrieve,
not conceal it indefinitely.  Some algorithms are meant to conceal just
until the message is delivered, some to conceal for days, and some for
years, none shield for centuries, but attempts are being made daily.

	Moreover as encryption algorithms become better understood, the
applicable means to break encoding become more numerous, and the power
of the computer (about 100Billion times more powerful today than in
1967) make encryption less and less secure at all levels.  Of course
computer speed also lends more encryption methods to the person
shielding information as well, but that is basically an efficiency
algorithm, not applicable to the direct computation of breaking any
particular code.

	Alternate languages are the best bet.  It is impossible to replicate
the cultural differences on a computer (at least that is true today I
think), so languages have distinct attributes that lend them to
expressing ideas in a different cultural idiom, and until the language
and/or culture are known, it is unfathomable, unless you find a decoded
bit that you understand (the rosetta stone for example).  Navajo code
talkers were used by the US military for that same reason in the Second
World War.

	If you are a number or math nut, encryption, prime numbers, fibbonacci
numbers, and transforms of all varieties will be a really interesting
topic of study.  

	Your signature says that you are a professor of political science.
Think about the political and cultural evolution of language, and then
think of encryption as a means to code the thoughts of one culture to
make it unique.  What forces act on that to keep it quiet, and what
forces work to weaken the culture. That is a form of code breaking.

Regards,
Les H


On Wed, 2009-09-02 at 21:34 -0500, Paul Johnson wrote:
> On Wed, Sep 2, 2009 at 3:32 PM, Dean S. Messing<deanm at sharplabs.com> wrote:
> > I have a terebyte sata drive that I need to securely wipe clean.  It
> > originally had 2 partitions.  I deleted them using `fdisk', rebooted,
> > and then as root ran
> >
> >    shred -vz /dev/sdd
> >
> > The drive is capable of about 60MB/sec, but shred is only "shredding"
> > about 25MB every 5 seconds according to its output.  Since the default
> > number of passes is 25, this works out to about 5 days.
> >
> 
> I have been reading this thread wondering this: why do we have to
> shred the whole disk, why not just find the parts that are actually
> used and write over them a few times.  I seriously doubt you have 1
> terrabyte of precious data.
> 
> Another idea just hit me.  What if you encrypt the data on the disk.
> Ubuntu has that thing now to create a Private encrypted partition.  Do
> that, move your precious stuff in there.  then unmount.   That is
> supposed to be just about impossible to recover, even for the NSA
> kids.
> 
> Anybody know if it is easier to crack an ecrypted file system than
> recover shredded data?
> 
> pj
> 
> --