MRAM, persistance of memory

[Eric Murray]

On Thu, Jul 10, 2003 at 04:45:58PM +0200, Thomas Shaddack wrote:
> On Wed, 9 Jul 2003, Eric Murray wrote:
> > I doubt it as well.  DRAM also has power-off memory persistence
> > and nearly everyone in security ignores that as well.
> >
> > But not the spooks :
> >
> > "The FEI-374i-DRS is a data recovery system that captures and preserved
> > digital data, in its original format, directly from the Dynamic Random
> > Access Memory (DRAM) of Digital Telephone Answering Machines (DTAMs)
> > ..
> > The FEI-374i-DRS is an indispensable tool for forensic investigators
> > required to evaluate residual audio and tag information retained in
> > today's DRAM-based DTAMs."
> >
> > http://www.nomadics.com/374idrs.htm
> 
> The system doesn't seem to be able to recover data from powered-off DRAM.

[..]

It's still interesting. 


> It is impossible to get access to the voltage on the DRAM cell capacitors
> (at least if the chip is in its case and we can access only its pins). We
> can only see if it is in the range for H or L. And after a power-down (or
> even a sufficiently long period without a refresh of the given cell) the
> cell capacitor loses voltage steadily, reaching the level of L (or maybe
> H?) within at most couple seconds.

I would not bet on that for sensitive data.
See Peter Gutmans and Ross Anderson's papers on RAM memory remanance.


Eric