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Comment by lutusp | Hacker News Reader

In engineering terms, it's easier to use a reversed-biased diode as a noise source. An input circuit would transfer the diode's random waveform into a shift register as zeros and ones, until the desired word size has been assembled.

It's really quite simple, and it could produce a very high degree of randomness. It would differ from typical PRNGs in that the binary sequence could not be reproduced, no matter how much you knew about the circuit.

> I have often wondered about this but lack the 'propriate schoolin'.

That's an easily remedied problem. Remember what Mark Twain said: "I have never let my schooling interfere with my education".

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Yeah, but AI is taking most of my free cycles at the moment. Still learning, but not much formal computer science. Thank you for responding.

> Yeah, but AI is taking most of my free cycles at the moment.

Given the present state of technology, that's probably a better use of your time. Someone else can produce a white noise source and mass-market it.

In engineering terms it would be easier to cover a shitty webcam with a bag, take a photo, and then use the lower bit of each pixel as the source of entropy.

You can use other things, like microphone input, or CPU temperature.

No need to buy expensive hardware generators.

Then you can use something like Fortuna to generate more random numbers from that seed:

http://en.wikipedia.org/wiki/Fortuna_(PRNG)

> You can use other things, like microphone input,

There's now been reported a way to hack a computer by way of its microphone, so that particular method is out.

> or CPU temperature.

CPU temperature doesn't change enough to serve as a secure source of entropy.

> No need to buy expensive hardware generators.

In fact, there are plenty of projects meant to locate sources of entropy to provide more randomness for computer security purposes. The idea of a hardware source like a reverse-biased diode is just one example.

> Then you can use something like Fortuna ...

Interestingly, the Fortuna scheme relies on system sources of entropy other than its own resources to assure security.

> There's now been reported a way to hack a computer by way of its microphone, so that particular method is out.

No, it's not. It's in some server in a datacenter. If you can get to the server, you can just change the Poker code, no need to do any crazy microphone hacking. Plus you'd need to know exactly when and how the microphone was sampled.

> CPU temperature doesn't change enough to serve as a secure source of entropy.

Doesn't matter how much it changes, the lowest bits are random on a large enough time scale.

You can just run the sampler until you get enough bits, it will take a few minutes. Or you can run it constantly and add more and more entropy as you go.

> > There's now been reported a way to hack a computer by way of its microphone, so that particular method is out.

> No, it's not.

Excuse me? Here's the source:

http://www.scientificamerican.com/article/computers-can-be-h...

Here's a quote: "Computers Can Be Hacked Using High-Frequency Sound -- A computer's microphone and speakers can covertly send and receive data"

Which word didn't you understand?

>> CPU temperature doesn't change enough to serve as a secure source of entropy.

> Doesn't matter how much it changes, the lowest bits are random on a large enough time scale.

False. Computer temperatures aren't a decent source of entropy, because they're too likely to remain stable for long periods. And the temperature can be predicted on a daily basis, a dangerous property for a secure source. That's why this source isn't used.

"by distances of up to about 65 feet (20 meters)"

Good luck getting that close to a server in a data center.

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