Randomness, Quantum Mechanics - and Cryptography

[Marsh Ray]

On 09/06/2010 09:49 PM, John Denker wrote:
>
> If anybody can think of a practical attack against the randomness
> of a thermal noise source, please let us know.  By "practical" I
> mean to exclude attacks that use such stupendous resources that
> it would be far easier to attack other elements of the system.

Blast it with RF for one.

Typically the natural thermal noise amounts to just a few millivolts, 
and so requires a relatively sensitive A/D converter. This makes it 
susceptible to injected "unnatural noise" overloading the conversion and 
changing most of the output bits to predictable values.

Using digital outputs from an enclosed module with enough shielding 
could probably prevent it. But there are plenty of environments which 
are too small (e.g., smart cards) or are potentially in the hands of the 
attacker for an extended period of time (smart cards, DRM devices, power 
meters, etc.).

- Marsh

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