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Re: Does reboot clear RAM?

From: Narcis Garcia
Subject: Re: Does reboot clear RAM?
Date: Wed, 13 Nov 2019 09:58:08 +0100

El 13/11/19 a les 7:27, Joachim Durchholz ha escrit:
> Am 12.11.19 um 02:20 schrieb Jakob Bohm:
>> On 11/11/2019 20:27, Joachim Durchholz wrote:
>>> Am 11.11.19 um 15:35 schrieb Jakob Bohm:
>>>> On physical machines, the following mechanisms are common:
>>>> 1. DRAM chips physically loose their contents after a few seconds of
>>>> power
>>>>    off,
>>> I am by no way an expert, but the forensic experts tell me that data
>>> can persist for *minutes*.
>>> Of course, the first bits flip after a few seconds. But you don't get
>>> a guarantee that everything is zeroed.
>>> I also hear that temperature plays a really big role here.
>> There's a difference between reading faded bits with special analogue
>> equipment
>> after artificially cooling chips way below what the datasheet allows, and
>> reading the digital bits at normal temperature, voltage etc.
> The refresh circuitry of a DRAM chip is just for the purpose of reading
> faded bits.
> And of course it will read whatever it decides is in the cell. If enough
> electrons are left, it will be above the threshold, so you can expect to
> see the occasional 1 bit in RAM unless it's cleared.
> I'm still interested in hearing whether typical RAM has a RST line and
> whether that wipes memory (or merely initializes internal circuitry).
> Speculation about potential low-level circuit trickery is nice but does
> not answer that question, I fear.

I think the best solution is to implement:
- A flag/parameter to reboots do clear RAM
- A flag/parameter to reboots don't clear RAM
- A default behaviour.

Default behaviour could depend on specified chipset or other virtualized
hardware if that originally have different behaviour.

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