

Ensuring Randomness with Linux's Random Number Generator - jgrahamc
http://blog.cloudflare.com/ensuring-randomness-with-linuxs-random-number-generator?

======
js2
There's a mention of lava lamps as a source of entropy... Here's the history
on that:

[http://en.wikipedia.org/wiki/Lavarand](http://en.wikipedia.org/wiki/Lavarand)

See also [http://www.lavarnd.org/](http://www.lavarnd.org/)

Meta - noticed two typos:

1\. "By hashing the entire pool _and and_ some"

2\. "and how they _effect_ (should be affect) programs"

~~~
eastdakota
Thanks. Typos fixed.

------
yuvadam
Funny anecdote: every time I cat /proc/sys/kernel/random/entropy_avail the
value drops. It slowly rises when the usual entropy sources are used
(mouse/keyboard/IO).

Can anyone explain the consistent value drop when cat'ing?

~~~
gizmo686
I can't explain your observations. On my machine, I tried cat`ting
entropy_avail every .1s. My observation it that in consistently rises until it
hits 190, when it instantly drops to around 140. The upper bound of 190 seems
to be pretty consistent (very occasionally it drops earlier, it never seems to
exceed 191), where the lower bound goes between 130 and 160. I'd assume this
means that I'm low on entropy (especially because the post indicates that
below 200 indicates that the system is running low), however I cannot think of
anything special I am running that would be eating entropy. Also, mashing my
keyboard and mouse does not seem to affect the rate of entropy accumulation.
Decreasing my sample rate also does not seem to slow down the rate of
accumulation, so it looks like cat`ing does not affect the value on my
machine.

------
gus_massa
Slightly off topic:

 _> (As an aside, pi is an example of a normal number: one where all the
digits will appear in equal quantities)._

From the linked Wikipwdia article:
[https://en.wikipedia.org/wiki/Normal_number](https://en.wikipedia.org/wiki/Normal_number)

 _> For example, it is widely believed that the numbers √2, π, and e are
normal, but a proof remains elusive._

------
deathanatos
> For example, if you’re reading this using a link to
> [https://blog.cloudflare.com](https://blog.cloudflare.com) then the SSL
> connection you are using will have required random numbers to ensure its
> security (they were used as part of the establishment of the secure
> connection).

 _If._ Raises the question of why the HN link isn't HTTPS.

------
pontifier
I've recently been dealing with the question of low entropy with some virtual
machines. I decided to delay installation of the ssh server until after I was
able to boot up and bang on the keyboard in a text editor to get the entropy
over 2000.

------
Qantourisc
All your efforts are in vain, you are located in the USA...

