[TriLUG] OT: Linux Friendly Laptop Forsale

[Aaron S. Joyner]

You are quite correct, alternating bit patterns tend to mess with even 
the data between the bits, which is where "residual" information can 
often be recovered by an infinitely determined and funded individual.  
Unfortunately, *logically* alternating bit patterns may not really 
equate to *physically* alternating bit patterns on the actual platters.  
Because modern disk drives may use unconventional ways of writing to the 
platters, such as proceeding through them in a helical pattern, as 
opposed to a linear one.  Some discs even use more elaborate patterned 
writing in attempts to improve access and read/write times.  It would 
probably be best to read up on the memtest86 scanning method, and employ 
something similar to the patterns he uses for testing, as a wipe 
method.  Bearing that in mind is why I chose /dev/random for my example, 
as opposed to /dev/zero, but as you illustrate there is a lot more that 
can be done in the name of being thorough.  Consider the rumored NSA 
practice, which is actually shooting a lead slug into the platters, 
physically destroying the entire device.

Aaron S. Joyner


john mitchell wrote:

> For the truly paranoid:
>
> fill entire disk with 0x55.
> fill entire disk with 0xAA.
>
> repeat 10 times.
>
> (the alternating bit patterns really jam's it up for the NSA types)
>
> john mitchell
>