It works!

The Photonic has only been crudely assembled, but we couldn't wait to test it. Not all the bolts have been tightened properly, and some of the soldering is of suspect quality but it runs. So this is the output it produces at a rate of about 10 frames /s...

Working Photonic/photonic-entropy.jpg

Working Photonic/Photonic-entropy-2.jpg

Working Photonic/Photonic-entropy-3.jpg

Exciting is not the word.

Before negative waves make themselves felt, look very carefully at the three images. They are not just black squares (although there is some dependence on your individual monitor screen characteristics). All three images are different. The noise pattern changes with every snapshot from the web cam. The images are consistent with the earlier first webcam output

The randomness extractor is a variable block size hash function that Helen developed. It can accommodate input blocks up to 65534 bytes (524272 bits), is based around a Pearson Hash and works on the substitution permutation network principle.

A couple of thousand frames were processed, extracted from and a sample file generated for a Diehard randomness test. It passed. The Diehard output is in the attachments, with no individual test failures or improbable standard deviations. There is also an ent randomness test output. It contains good chi and pi scores suggesting randomness. The fact that ent was run over a 10993740 byte file instead of the more traditional 500 KB should not cause concern. All it's statistical tests are file size independent and valid for any file <2GB at which point it's 32 bit programming produces wildly incorrect results.

A true random number generator has to satisfy the golden rule of outputting less entropy than it generates, otherwise it's just a pseudo random number generator. We measure the entropy of the Photonic output with our little gauge:

Working Photonic/Min.Entropy-Gauge.png

This utility calculates the minimum entropy[1] of the JPEG files produced by the web cam according to the standard formula:

Working Photonic/Hmin.png

We absolutely really really positively do not unpack the JPEG files into image rasters. That is a frequent and fundamental error developers of web cam based random number generators make. You will see that each frame contains approximately 100,000 bits of pure entropy. This varies somewhat due to several factors. At a frame rate of 10 per second, the Photonic Instrument can produce 1 MBit /s of raw entropy prior to randomness extraction. No too shabby and is a tenth of the generation rate of some commercially available quantum based random number generators[2]. They do come in somewhat smaller boxes though as we were constrained by having 8 no. M12 bolts in Paul's design.



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Kind Attachment Name Size Version Date Modified Author Change note
Hmin.png 10.1 kB 1 06-Jan-2017 02:15 Helen
Min.Entropy-Gauge.png 13.1 kB 1 06-Jan-2017 01:13 Helen
Photonic-entropy-2.jpg 21.0 kB 1 06-Jan-2017 01:22 Helen
Photonic-entropy-3.jpg 21.0 kB 1 06-Jan-2017 01:22 Helen
camera.out.txt 20.8 kB 1 06-Jan-2017 01:14 Helen
ent.out.txt 0.5 kB 1 06-Jan-2017 01:40 Helen
photonic-entropy.jpg 20.9 kB 1 06-Jan-2017 01:17 Helen
« This page (revision-) was last changed on 06-Jan-2017 02:47 by Helen
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