Re: Continuing /dev/random problems with 2.4

Peter Monta
2002-02-02T03:30:50Z

H. Peter Anvin wrote:

> However, those aren't the main failure modes you need to be concerned
> with. Antenna effects may actually be your biggest problem -- picking
> up deterministic signals from other parts of the system.

David Wagner wrote:

> For instance, is there a risk that the audio data you read is strongly
> correlated to 60Hz mains noise in some scenarios? ...

I don't think predictable elements in the audio hurt anything.
So long as there is a noise component, things are fine.

Take the case of a half-full-scale 60 Hz sine wave plus a tiny
bit of noise. No problem---each sample would still be worth
0.1 bit because the attacker can only guess the 60 Hz part:
subtract this out and you've still got unpredictable noise.
Same deal with crosstalk between channels, so long as it's
reasonably small, say -20 dB or better (as it will be with any
sane sound chip).

> [ audio-entropyd ]

Aha, nothing new under the sun.

Cheers,
Peter Monta