Would take '1018 times the age of the universe' to guessBy Richard Chirgwin, 30 May 2014
Your smartphone is a quantum device that can be used to generate truly random keys, according to boffins at the University of Geneva.
The Swiss research finds, quite simply, that illuminating the camera of a device like the Nokia N9 can cause quantum effects that can be used to generate keys – in effect making the smartphone a quantum random number generator (QRNG).
That's a lot cheaper than the QRNG kit currently on offer – although it's more expensive than visiting the ANU's https://qrng.anu.edu.au/RainBin.php online QRNG site.
The attraction of using quantum effects is simple: quantum noise is truly random, and unlike pseudo-random number generators (PRNGs), they're not weakened by how the maths of PRNGs work. The trick is in the implementation – how quantum noise is detected, isolated, and digitised as a number, which is why QRNGs are expensive.