Re: Why does reading from /dev/urandom deplete entropy so much?

[Ray Lee]

On Dec 11, 2007 11:46 AM, Phillip Susi <psusi@xxxxxxxxxx> wrote:
> Theodore Tso wrote:
> > Note that even paranoid applicatons should not be using /dev/random
> > for session keys; again, /dev/random isn't magic, and entropy isn't
> > unlimited. Instead, such an application should pull 16 bytes or so,
> > and then use it to seed a cryptographic random number generator.
>
> What good does using multiple levels of RNG do?  Why seed one RNG from
> another?  Wouldn't it be better to have just one RNG that everybody
> uses?

Not all applications need cryptographically secure random numbers.
Sometimes, you just want a random number to seed your game RNG or a
monte carlo simulator.
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