>One of the problems is for example to get a suitably random number
>soon after booting an embedded device, without external activity.
>A PRNG is no good here - the sampling occurs at quite predictable
>time since the power was applied.
Yes, that's why Andy needs to check multiple samples gathered
On 17.01.2012 23:55, Peter Waltenberg wrote:
> I think my point is valid though - even if it is a PRNG, provided it's a
> good one (and distribution will tell you that) if an attacker can't tell
> exactly when you are sampling the PRNG effectively it's a usable entropy
> source.
One of the proble
On 17.01.2012 22:47, Andy Polyakov wrote:
> Come on, having me preparing bootable CF card image for a gizmo I'm not
> familiar with is unrealistic. Don't you have anything you can compile
> 10-lines C code and some assembler to add to?
Well you mentioned tests on x86 in your paper, I thought you
Depends on the PLL design - which we don't know. But yes, generally they
are notoriously sensitive to thermal effects.
I think my point is valid though - even if it is a PRNG, provided it's a
good one (and distribution will tell you that) if an attacker can't tell
exactly when you are sampling the
>> The single user case, a lot less confident, yes, PLL's tend to be noisy
>> devices, and may well be behaving like a real entropy source here, however
>> my EE background is 20 years old, and things may have changed - plus, you
>> don't really know what the source of the noise is, that'd require
>> If you know anybody (or if there
>> is anybody reading this) who can conduct such experiment, i.e. on such
>> wide temperature range, on any computer (but ARM)
>
> Unfortunately only ARMs in a suitable form-factor here :(
>
> In case you have something directly bootable from a CF card on
> a P
On 17.01.2012 21:52, Andy Polyakov wrote:
>> Out of curiosity: Does the picture change if you are running the test
>> hardware in a refrigerator at -20 degrees celsius and at say
>> 40 degrees? ;)
>
> Do *you* keep your systems in fridge? If so, how do you deal with
> condensate when you take the
> Out of curiosity: Does the picture change if you are running the test
> hardware in a refrigerator at -20 degrees celsius and at say
> 40 degrees? ;)
Do *you* keep your systems in fridge? If so, how do you deal with
condensate when you take them out (or even open the door)? I mean, no, I
can't o
On 17.01.2012 16:52, Andy Polyakov wrote:
> Maybe relevant question is not how [in]predictable is PLL's reaction on
> input frequency variation, but that there is one. I mean even if PLL
> reaction is predictable, *when* [thermal] variation and consequent
> reaction occurs is not, right?
Right, i
> In praxis the feedback loop will exhibit both deterministic
> (e.g. quantization) and random (thermal) noise. For example
> if the common input clock changes, feedback loops in both
> PLLs go through their transfer functions until they stabilize
> on the new frequency. The resulting jitter will p
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