[Cryptography] Lava Lamps Can Actually Create Secure File Encryptions - Here's How

[Charles Jackson]

> 
> On 3/4/26 2:30 PM, Jon Callas wrote:
>> The effect works better in the dark, of course because when there's a lot of light it washes out the noise. Nonetheless, it's easy to adjust ISO, use ND filters (or even better, IR filters). You just want sensor noise, that's all.
I don’t think that is quite right.  Light is often modeled as a poisson process with the intensity of the light corresponding to the average value of the poisson process during the exposure time.  The noise has a standard deviation equal to the square root of the intensity.  So, as the intensity increases the ratio of the signal power to the noise power increases—but the noise increases also.  A moderately illuminated grey card imaged with a modern camera could easily be adjusted so that the mean value was 10 bits (1024).  In this case the lower 5 bits should be quite random.  If you xored bits 1, 2, and 3 you would probably get a highly reliable random 0-1 value.  I think that a modern camera, say a Nikon Z8, shooting raw would be a good random number generator if used in this fashion.  

That said, the above quoted statement is correct in the sense that an image of a bright scene will saturate.  In some cases it will just yield the max number possible (say 2^14 - 1) at most or all pixels.  In other cases it will yield a number related to the size of the electron well at each pixel sensor.  So, if the choice is between maximum dark and maximum bright, go with maximum dark.  There would be good chance that the lowest one or two bits would be random.  

Here is a pretty accessible source on the physics and engineering of camera sensors:  https://www.photonstophotos.net/GeneralTopics/Sensors_&_Raw/Sensor_Analysis_Primer/Sensor_Analysis_Primer.htm. 



Chuck






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