memory pages nulling when releasing

[Dan Lukes]

Dag-Erling Smørgrav napsal/wrote, On 06/19/06 13:49:
> I very much doubt it.  DRAM needs to be continuously refreshed, and
> loses its state within milliseconds of losing power.
> 
>> At least I saw that in TV (CSI Wanne-Eickel or so), how they read from a
>> overwritten hard disc shreddered with a "laser"...
> 
> Umm, first, CSI is fiction; second, unlike DRAM, a hard disk is
> designed to retain information when power is switched off.

	Well, we should not accept fiction serials as serious source of 
information. On the other side, we know nothing about secret services 
secrets. Sometime, the more safe side is count that they MAY be able to 
do it (despite of exact meaning of "they" and "it").

	I know something about not so secret secrets. You need no physical 
access to computer nor active remote access. You need no steal the DRAM. 
The computer is big transmitter of electromagnetic waves which can be 
received from distant place. Analysis of it can not so unimportant part 
of the computers work. As distant passive method it's almost undetectable.

	Counter-measures against this kind of spying is very expensive - you 
need special isolated server room and large controlled area with 
restricted access around it (even the best isolated room can't shield 
the transmission completely).

	I don't dispute about probability that someone asking this kind of 
question in this kind of discussion list has sensitive data of high 
value for a secret service (and obtainable by know technique of 
receiving elmg. noise or unknown technique of reading of upowered DRAM).

	On the one side, price of counter measures should be comparable with 
risk value. Zeroing some memory containing selected sensitive data as 
part of free on application level is very cheap solution. It's eligible 
even in the case the value of eliminated risk is very low, so we should 
not deny it as technique with no real value ...

						Dan


-- 
Dan Lukes                                   SISAL MFF UK
AKA: dan at obluda.cz, dan at freebsd.cz,dan at kolej.mff.cuni.cz